The ultimate examples of how the "next man up" can make or break an NFL team are two recent Super Bowls. Last season, we saw the Chiefs lose various starting offensive linemen throughout the season, but when Eric Fisher tore his Achilles in the AFC Championship Game, the dam broke. Andy Reid & Co. couldn't protect Patrick Mahomes, who spent most of the day running for his life in a frustrating loss to the Bucs. No team may have been able to deal with as many injuries as the Chiefs did up front, but it's clear that the combo of Mike Remmers and Andrew Wylie wasn't the answer.

Go back a few years, though, and you get the opposite example. Carson Wentz's near-MVP campaign carried the Eagles through most of the 2017 regular season and into the top seed in the NFC, but when Wentz tore his ACL, Nick Foles was there to pick up the slack. Foles was a mess in his final two starts of the regular season, but in three playoff games, he threw for 972 yards with six touchdowns. Having a viable option to replace Wentz helped save Philly's season and win the Eagles a Super Bowl.

In the salary-cap era, just about every team has a hole in its starting lineup, let alone behind those starters. Let's look at the most obvious points of vulnerability around the NFL and see what organizations would be forced to do if they lost their starter at a key position.

Naturally, a fair number of these players are quarterbacks, but as we saw with the Chiefs last season, losing player(s) at another position can be enough to make or break your year. For positions in which a team starts two or more players, I'll look at the players who back up the primary starter I'm discussing, as opposed to the other starters around him. Unsurprisingly, though, I'll begin with a signal-caller:

Next up: Logan Woodside, DeShone Kizer

Let's start with the most obvious point of concern for a contending team. Tannehill's work with the Titans has exceeded any and every expectation since the former Dolphins quarterback came over from Miami on a salary dump in 2019. Tannehill has been both wildly efficient and readily available. He missed 21 games over his final three seasons in Miami with knee and nerve issues, but he hasn't missed a game since taking over as Tennessee's starter.

Outside of a brief moment in which he stumbled while celebrating a touchdown, the Titans haven't had to even think about turning things over to another quarterback. If that changes, Tennessee would be in serious trouble. Its backups at the moment are, at best, question marks. Woodside was the 249th pick in the 2018 draft and has just three career pass attempts, while Kizer has posted a 58.9 passer rating across stints with the Browns and Packers.

The Titans got by last season without needing to turn to Woodside for meaningful action, and they might be able to do so again in 2021, but losing Tannehill would leave a win-now team with one of the worst quarterback situations in the league. Mike Vrabel's team is one of the most run-heavy offenses, so you might be able to make a case that they could get by with Woodside or Kizer by leaning on the talents of Derrick Henry. Then again, given that the backfield behind Henry consists of Darrynton Evans, Brian Hill and Jeremy McNichols, the Titans might be in similarly rough shape if Henry were to go down. Tennessee's top-level talent is undeniable, but it will need its stars to stay healthy to live up to expectations.

Next up: Cooper Rush, Ben DiNucci, Garrett Gilbert

The downside for a top-heavy team that sees its stars get injured is the 2020 Cowboys. Dallas lost free-agent signing Gerald McCoy in training camp and then saw its offensive line fall apart, as star tackles La'el Collins and Tyron Smith combined to play just two games, while Zack Martin missed the better part of eight contests. Things looked bleak and then got worse when Prescott, who hadn't missed a single pro start, suffered an ankle injury in Week 5 and missed the remainder of the year.

Prescott was replaced by Andy Dalton, who couldn't do much behind a patchwork line. Prescott and his starting linemen are back in 2021, but if the Cowboys lost him yet again, they wouldn't be able to call on somebody as accomplished as the Red Rifle. Their backups this season have a combined 80 career pass attempts, yielding a 52.5% completion percentage while averaging 5.2 yards per attempt. Offensive coordinator Kellen Moore might have been a better option than DiNucci and Gilbert for spot starts last season, and the Cowboys won't want to find out whether those backups have improved in 2021.

Next up: Michael Jacquet, Zech McPhearson, Kevon Seymour

Cornerback is a little different since a team will use two or three corners on any given snap, but let's stick in the NFC East and look at a team that got what it wanted and might end up regretting it. After years of skimping on cornerbacks and emphasizing depth over top-level talent, the Eagles went out to get the No. 1 corner that fans had been clamoring for last offseason and traded for Slay, who signed a three-year extension in the process. Slay was inconsistent in his first season with the Eagles, who fell apart around the talented corner.

Now, in part because of how much it's paying Slay, this team is perilously thin at corner. Hybrid defender Avonte Maddox might start in the slot, but the depth chart at cornerback around Slay is one of the weakest in the league. The Eagles are looking at replacement-level corners, practice-squad guys and rookie fourth-round pick McPhearson to compete for jobs on the outside. Good corners can come out of nowhere sometimes, but teams don't want to be counting on stumbling upon a useful player before the season even begins.

If Slay is a shutdown corner in his second campaign in Philly, new defensive coordinator Jonathan Gannon will have to worry about one side of the field on every snap. If Slay isn't impressive or gets hurt, there might be no place for these corners to hide, particularly in a division with wideouts such as Amari Cooper, Kenny Golladay and Terry McLaurin.

Next up: Barkevious Mingo, Jacob Tuioti-Mariner, Adetokunbo Ogundeji

Like Slay, Fowler was a long-awaited addition who didn't live up to expectations in his new digs, with the former Jaguars and Rams pass-rusher getting just three sacks in a disappointing season with Atlanta. Those three sacks were still good enough to tie for third on the team behind middle linebacker Deion Jones and star defensive tackle Grady Jarrett, with the Falcons failing to field a single player who racked up even five sacks in 2020.

Defensive coordinator Dean Pees will have to get more out of his star edge rusher in 2021. Fowler missed two games last season, and if he's unavailable for any stretch of time this upcoming year, the former Patriots and Titans assistant would be down to bare bones on the edge. Jarrett can hold down the middle, but the Falcons would be looking at journeymen such as Mingo and Jonathan Bullard competing with midround picks on the outside. This cap-strapped Atlanta team sorely needs to add more help on the edge.

Next up: Jalyn Holmes, Patrick Jones, Janarius Robinson

Did you see what happened with the Vikings in 2020? Hunter missed the entire season with a neck injury, and while they had Yannick Ngakoue on the roster to start the season, the organization gave up on the former Jags star and traded him to the Ravens at midseason. Minnesota finished with the league's fifth-worst adjusted sack rate and was third worst in the NFL at getting pressure without blitzing.

Hunter is back, and after agreeing to a revised contract, the 26-year-old is expected to report to training camp and be on the field to start the season. He has been hugely productive when available, but the Vikings would be lost again without their star pass-rusher. Minnesota did add Sheldon Richardson this summer, but an edge duo of Holmes and Stephen Weatherly doesn't have enough pass-rushing talent. The Vikings used midround picks on Jones and Robinson, but they shouldn't be counted on for significant contributions in their rookie campaigns.

Next up: Marquez Callaway, Deonte Harris, Lil'Jordan Humphrey

Thomas didn't miss the entire 2020 campaign, but the star wideout suffered a high ankle sprain in Week 1 and never recovered. He came back for a six-game stretch before returning to injured reserve and wasn't a difference-maker during the postseason. The Saints got by just fine on offense without the 2019 All-Pro, but that was with Drew Brees, Emmanuel Sanders and Jared Cook in the fold.

Brees, Sanders and Cook are all gone and replaced on the roster by players such as Trevor Siemian, Nick Vannett and seventh-round pick Kawaan Baker. Whether it's Jameis Winston or Taysom Hill at quarterback, whoever takes over as the starter will need Thomas on the field as the offense's chain-mover through the air. Tre'Quan Smith will start on the other side, but if Thomas misses time again, the Saints would be looking at Callaway & Co. to take on more significant target totals.

If they can somehow carve out some cap space, it wouldn't be a surprise to see them go after a veteran wideout at the end of training camp.

Next up: Geno Smith, Danny Etling

I would imagine most Seahawks fans can remember what things were like between the departure of Matt Hasselbeck and the arrival of Wilson, which is why I would imagine most of those fans didn't want to see the star quarterback leave town this spring. The Wilson rumors have subsided, and thankfully for Seattle fans, few quarterbacks in league history have his track record of availability. Through nine seasons, Wilson has yet to miss a game due to injury. The only other quarterback to start every one of his team's games through his first nine seasons as a pro is Peyton Manning.

Wilson has played through an ankle injury before, but if something more serious did happen, the Seahawks would probably find it tough to recover. Their primary backup is Smith, who lacks Wilson's mobility and has a career passer rating of 72.9. Etling and Alex McGough have bounced around the bottoms of pro rosters without throwing an NFL pass. The Seahawks would need to retreat into a run-heavy attack if Wilson went down, which might make Pete Carroll happy.

Next up: Vinny Curry, Kyle Phillips

The big-money free-agent addition for the Jets on defense this offseason, Lawson is going to be the primary pass-rusher for new coach Robert Saleh. The Jets are deep on the interior after adding Sheldon Rankins to play alongside Quinnen Williams this offseason, but if Lawson disappoints or gets injured, they don't really have a Plan B on the edge.

Curry was a useful piece for the Eagles for stretches, but he's a rotational edge at this point of his career and doesn't have Lawson's athleticism. Having a healthy "Leo" lineman is essential for Saleh; consider that his 49ers fell from second in adjusted sack rate with Nick Bosa in the lineup in 2019 to 24th a year ago, when Bosa tore his ACL.

Next up: Trace McSorley, Tyler Huntley

The Ravens have had brief glimpses into life without Jackson over his first two-plus years as a starter; Robert Griffin was forced into overtime for a game against the Chiefs during Jackson's rookie campaign, and we saw three different backups throw passes for the Ravens last season.

Griffin was the primary player off the bench for Baltimore, but if the Ravens lost Jackson this season, they would be forced to turn to McSorley as their new quarterback. The former Penn State player was 3-for-10 last season. One of those passes was a 70-yard touchdown to Marquise Brown, although Brown did most of the work on the play.

Next up: Cassius Marsh, Quincy Roche

With the Steelers losing Bud Dupree to the Titans in free agency, Watt suddenly looms large atop the depth chart in Pittsburgh. He is a Defensive Player of the Year candidate, and 2020 third-rounder Alex Highsmith impressed as a rookie when he was forced to fill in for Dupree. In an organization that has no peer when it comes to drafting and developing defensive players, the starters look just fine. Behind those two? Not so much.

Owing to their cap issues, the Steelers weren't able to add much on the edge and used most of their draft picks to supplement a flailing offense. Marsh played for three teams last season and is on his eighth roster. Roche is a rookie sixth-round pick, and while the Steelers bring plenty of linebackers through their system, those guys are usually taken in the first couple of rounds. Any sort of change to Watt's status would leave a win-now Pittsburgh team in a vulnerable situation. Highsmith is a promising player, but would he really be ready to be the best edge rusher on a Super Bowl contender?

Next up: Roderick Johnson, Charlie Heck, Geron Christian

The Tunsil trade in 2019 might have kicked off the chaos in Houston, but as the Texans rebuild their organization after the past two years, it's worth remembering that the man himself is still around. That deal will go down as disastrous for the Texans -- and I don't know who will actually be playing quarterback over the next couple of years in Houston -- but Tunsil should do a good job of protecting whoever takes those snaps.

New coach David Culley could consider moving Tytus Howard to the left side if Tunsil were to go down, but the Texans would have one of the worst tackle situations in the league if it weren't for their expensive addition.

Next up: Antwaun Woods, Robert Windsor

The Colts sent a first-round pick to the 49ers to acquire Buckner before the 2020 draft, and the former No. 7 overall pick delivered on expectations. He racked up 9.5 sacks and 26 knockdowns in his first season in Indy despite missing a game while he was on the COVID-19 list. Buckner is one of the most expensive defenders in the league, but that's the sort of production teams are hoping to get from their top interior pass-rusher.

With question marks on the edge after Justin Houston left in free agency, though, the Colts desperately need Buckner to be that sort of force once again in 2021. Their sack rate and pressure rate were both unsurprisingly higher with Buckner on the field, while the passer rating they allowed rose from 85.3 with him on the field to 107.2 without their star tackle. Fellow starter Grover Stewart isn't a pass-rusher, and the Colts lost useful interior rusher Denico Autry to the Titans in free agency.

Next up: Derek Carrier, Foster Moreau

The best move from the Jon Gruden-era Raiders was acquiring Waller, who has emerged as one of the most valuable players in football. Over the past two years, the only tight end in Travis Kelce's neighborhood has been the Vegas star. They rank 1-2 in receptions and receiving yards, and No. 3 (George Kittle) is 64 receptions and 654 yards behind Waller.

The Raiders have high hopes for Henry Ruggs and their wideouts, but there's no way they could lose Waller without suffering a significant hit.

Next up: Uchenna Nwosu, Kyler Fackrell

Over his first five NFL seasons, Bosa has been a difference-maker. Los Angeles has posted a 6.3% sack rate with Bosa on the field, with that mark falling to 5.1% without their former first-round pick. Most of that came with Melvin Ingram in the lineup, but the 32-year-old left the organization this offseason and is as yet unsigned.

The only player the Chargers brought in to replace him was Fackrell, and while the former Packers linebacker had a fluky 10.5-sack season in 2018, he has 10 sacks over his four other seasons combined.

Next up: Chad Henne

OK, obviously, any team is going to drop off when they lose the most talented quarterback in the league. The more interesting discussion might be to consider whether other Chiefs would have a similar case. Travis Kelce just finished arguably the best season for a tight end in league history, and his backups are Nick Keizer and rookie fifth-rounder Noah Gray.

Likewise, if Tyreek Hill pulled a hamstring, the Chiefs would suddenly be looking at a wide receiver depth chart of Mecole Hardman, Demarcus Robinson, Cornell Powell and Byron Pringle. It's impossible to keep Mahomes off this list, and I'm trying to keep it to one player per team, but the Chiefs might have three of the most irreplaceable players in the league on one side of the ball.

Next up: Blaine Gabbert, Kyle Trask, Ryan Griffin

It only makes sense to finish up with the greatest ever, right? Brady helped immediately turn around an inconsistent Bucs offense in 2020, with the legendary quarterback growing more comfortable as the year went along before eventually winning his seventh Super Bowl. The Bucs have a ton of talent around him, but many of those same players were on teams with Jameis Winston and Ryan Fitzpatrick at quarterback, and those offenses were better in fantasy football than the real deal.

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Bart Scott says Tom Brady is attempting to cement himself as an all-time great athlete among the likes of Wayne Gretzky and Muhammad Ali.

Brady has been remarkably healthy during his career with two exceptions, both related to his knee. The future Hall of Famer left the AFC Championship Game in 2001 with a knee injury and then missed the final 15 games of the 2008 season after tearing his ACL in the opener. I don't see many signs that he's breaking down, but we just don't know when things will change. Remember that Brett Favre was a Pro Bowler as a 40-year-old in 2009 and brought the Vikings within one interception of the Super Bowl; a year later, his consecutive-games streak ended as a result of a shoulder injury, he threw more interceptions than touchdowns and he retired (for good) at the end of the campaign.

If Brady were to get hurt or fall off the proverbial cliff, the Bucs would be in rough shape. Gabbert is a Bruce Arians favorite, but the former Jags first-round pick has a 72.3 career passer rating. Tampa drafted Trask in the second round to eventually replace Brady, but it would be asking a lot for the former Florida signal-caller to step in as a rookie and take over for the most accomplished player in league history. The good news for the Bucs is that they probably won't need to find out what's behind those other doors.