Sunday night offers a past-vs.-future NFL matchup, with Tom Brady's Patriots visiting Lamar Jackson's Ravens. And while "past vs. future" is an oversimplification given the significance of both of those players to the league's present, you get the point. Brady's brilliant career is far closer to its end than its middle, and Jackson's to-be-determined career is in the middle of its thrilling start.

So there'll be time to write about Jackson, which means this week we'll focus on the Brady end of this. Adam Schefter's recent reporting has cast some doubt on whether Brady will play for the Patriots -- or at all -- after this season. He's 42 years old, a six-time Super Bowl winner with nothing left to prove and no contract beyond this season.

But he's not alone. In New Orleans, quarterback Drew Brees is 40 and is not signed beyond this season. The Chargers' Philip Rivers is 37 and in the final year of his deal. Pittsburgh's Ben Roethlisberger is also 37, and while he has years left on his contract and intends to play in 2020, he's out for the rest of the season with an elbow injury. There's no guarantee he makes it back, and if he does, there's no guarantee how much longer he'll play.

These are stalwart quarterbacks -- linchpins of the early-21st-century NFL. With the exception of Rivers, they have all been champions. Along with former Colts and Broncos quarterback Peyton Manning, who has been retired for a couple of years now, they have spearheaded the current era of passing-game dominance. And their time in the league is nearing its end.

What will the NFL look like once these guys are all gone? It's all speculation, of course, but it's a topic of some degree of conversation around the league. Here are some parameters and best guesses on a couple of key questions:

What will their teams do?

The timing is key here. If Brady, Brees, Rivers and Roethlisberger all retire in 2020, it would be fascinating to watch a quarterback market that otherwise has a chance to be overloaded with imperfect but interesting options.

A partial list of quarterbacks who could be free agents at the end of this season includes not just Brady, Brees and Rivers but also Jameis Winston, Marcus Mariota, Eli Manning, Ryan Tannehill, Case Keenum and Teddy Bridgewater. A partial list of accomplished veterans who could be released from their contracts and made into free agents (depending, of course, on a lot of different circumstances -- don't get angry here) includes Cam Newton, Andy Dalton and Derek Carr.

Depending on how things shake out with Gardner Minshew in Jacksonville, the Jaguars could look into making him or Nick Foles available in a trade. If Alex Smith gets back healthy and wants to keep playing, Washington would have to see what it could get for him. Add all that to a 2020 NFL draft class that includes the likes of Tua Tagovailoa, Justin Herbert and Joe Burrow, and there is a stunning number of quarterbacks potentially available next offseason to potentially needy teams. Heck, after a year off, maybe Andrew Luck can be talked back into the league. Crazier things have happened, right?

The problem is, the landscape changes for the likes of the Pats, Chargers and Saints if their current future Hall of Famers decide to come back for a year or two or three. Then those teams would be stuck having to make their long-term quarterback plans amid uncertainty. Could the Saints persuade Bridgewater to stick around for another year or two as Brees' backup, or would Bridgewater want to cash in his 5-0 relief performance on a $20 million-plus-per-year deal? Would a veteran like Dalton be OK with backing up Brady in New England and helping develop Jarrett Stidham or some 2020 draft prospect as the eventual successor? If you're the Chargers, do you make a trade for, say, a Minshew if you don't know for sure at what point in the three remaining years on his rookie contract you'd need him to take over for Rivers?

Assuming Brees, Brady and Rivers all sign new contracts to stay where they are, that would give their teams some clarity that could help with those types of decisions. But if they all start going year-to-year on their deals, as Brees and Brady already have demonstrated a preference to do, then that clarity remains elusive. All of these teams could have difficult times over the next couple of years trying to implement succession plans while also still trying to respectfully manage -- and take advantage of -- whatever their iconic veterans have left to give them.

What will the players do?

Peyton Manning isn't exactly setting up a retirement blueprint for all-time great quarterbacks. "Insurance pitchman and ESPN+ football programming front man" isn't an avenue that's going to be open to just everyone. But it's interesting to imagine Brady, Brees, Rivers and Roethlisberger in their post-football lives.

The broadcast networks would probably write each one of them a blank check, and I can imagine any of them but Brady behind the microphone. (And who knows, maybe he'd surprise me.) But the trick is, you'd have to find a way to make it worth their while. The four of them together have earned a little less than a billion dollars in their careers from just their football salaries and bonuses -- which is to say nothing of their off-field endorsement income. They won't need jobs, and they're not going to sign up to do the No. 4 game in the weekly CBS rotation. You'd have to be talking about a Troy Aikman/Tony Romo-level type of job to entice these guys, and ... well, those jobs are of course taken.

When I covered the Yankees, Derek Jeter used to tell us he wasn't interested in getting into coaching or broadcasting when he was done playing but that he wanted to own a team. That is the path he took. And while it hasn't gone particularly well for him, it leaves open the possibility of other athletes who've made their fortunes going down similar paths. Could Brady and his much richer wife, Gisele Bundchen, end up with enough to buy a majority interest in an NFL team? Would they want to?

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Adam Schefter explains that Tom Brady will likely opt to play somewhere else next season or even retire, and strongly proclaims that Brady staying in New England is the least likely option.

A step or two down from that is the John Elway path. Elway isn't the Broncos' owner, but he is their team president and general manager. That's a role in which many have imagined Manning since his retirement, and perhaps he finds himself doing that for some team in the future. Perhaps one of his still-active contemporaries is thinking along similar lines.

And then there's the possibility that they just vanish, right? I mean, Rivers has nine kids. Would you be shocked if he retired and disappeared from the public eye? He'll certainly have more than enough to do.

What becomes of the quarterback position?

That's kind of where Lamar Jackson comes in, though he's not alone. The highest-paid quarterback in the league right now is Seattle's Russell Wilson, who's 30 years old and doesn't look as if he's almost done. Not far behind him are the likes of Carson Wentz and Jared Goff, and in the next year or so we're likely to see mega-extensions for the likes of Dak Prescott, Patrick Mahomes and Deshaun Watson. Newton is still kicking around in Carolina and in line for a big new deal if he gets back healthy. And we'll wait and see on the first-year and second-year signal-callers, on whom the jury is obviously still out.

Point is, the position isn't going to lack for big names and star power just because these all-time legends are walking away. The question everyone wants answered is one of longevity. The Luck retirement just before this season started threw the league for a loop and left it to wonder. Will someone like Mahomes, who's the brightest star in the league and looks set up to dominate for decades, even want to stick around as long as Brees and Brady have? Will youngsters like Watson and Jackson and Josh Allen, who run an awful lot more than their predecessors ever did, last long enough through the hits they're taking to have the same types of Hall of Fame careers?

Whenever it is that the stewards of this golden QB age decide to hang up their cleats, they will leave a lot of questions -- and a far different-looking NFL -- behind them.

Some other stuff I've been keeping an eye on around the NFL this week:

Looming health-related grievances

I'm told to expect the NFL Players Association to file multiple grievances against the Jets on behalf of offensive lineman Kelechi Osemele, who was released by the team last week following a dispute over his medical care and diagnosis. And I'm curious to see how the situation between Trent Williams and Washington proceeds from here. Williams spoke to the media Thursday, revealed that he'd had cancer and surgery to address it and offered some clarity as to exactly whom he does and doesn't hold responsible in the organization. The trade deadline having passed, Williams isn't likely to get a shot to play elsewhere until the offseason. If the team tries to release him and get out of paying his non-guaranteed salary, or if it tries to place him on the non-football injury list (which would allow Washington not to pay him), it will likely face a big-time fight from the player and his union.

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Trent Williams says team doctors failed to test a cancerous tumor on his head for six years before he was diagnosed.

We wrote a couple of weeks ago about players exercising their leverage when it comes to contract situations and not wanting to play for their current teams anymore. But this is an offshoot of that. There are situations around the league in which there are significant trust issues between teams and players. And as players grow more educated about their rights and their health, if they start to feel as if the team is acting against their best interests on medical matters, they can look to Osemele and Williams as examples of ways they can handle these matters without simply doing what the team tells them because they don't think they have any other options.

Young QBs and turnovers

I love watching Giants rookie Daniel Jones run and throw the ball. He's incredibly talented, and Giants fans have reason to be excited about his future. But great googly moogly does he have to stop turning the ball over. He has seven interceptions and eight fumbles (six lost) in six starts. This is a completely unsustainable pace, and the Giants are doing the player and their team a massive disservice if they don't make it a top priority.

I covered the Panthers' game Sunday in San Francisco, and while this may not be the best time to make this comparison because he threw three interceptions in that game, it's worth noting that Panthers quarterback Kyle Allen does seem to have figured out his fumble problems in a short period of time. Allen fumbled the ball five times in his first two games in relief of Newton this season, then once in his third and not at all in the two he has started since. (He also hadn't thrown an interception until he met Nick Bosa, Richard Sherman & Co. last weekend.)

"You have to drill it, you have to spend time on it," Panthers offensive coordinator Norv Turner told me, in discussing how he and his son Scott, the Panthers' QB coach, helped iron out Allen's fumble issues. "A lot of Kyle's fumbles came when he had one hand on the ball. So you have to stress that -- keep two hands on it. Elbows in, both hands on the ball, when you're forced out of the pocket, make sure you take three or four steps before you even think about pulling it back to throw it, because these guys are all faster than what you saw in college, and they're on you quicker, and they're trying to get that ball out of your hands.

"Cam has the biggest hands I've ever seen, and with him there are times when you think, 'How did he not fumble?' But when you have normal-sized hands you have to pay more attention."

Three things on the Bears

Chicago might be in as precarious a spot as any team this week. Headed to Philadelphia for a tough game against the Eagles, having already lost as many regular-season games as they did last season and sitting in last place in their division, three and a half games behind the Packers and two and a half behind the Vikings, the Bears not only need a win but need to get on a roll. Having talked with some people there this week, I believe these three things:

• They're determined to ride it out with third-year quarterback Mitchell Trubisky, since they believe in his upside and think they can get him fixed.

• They believe rookie David Montgomery can be a three-down feature back and they hope he stays consistent enough that they can use him as much as they did last week.

• They are concerned about the closing of a window. While pass-rusher Khalil Mack is a long-timer as a defensive anchor and second-year linebacker Roquan Smith looks as if he should be a keeper, there are some tough decisions coming up on some of their defensive veterans as their salaries grow larger and less guaranteed. This was a big year for the Bears, and it may already have slipped away.