Eighteen NFL teams open their mandatory three-day minicamps this week. Ten held theirs last week, with four teams electing to cancel. Teams that opted out of mandatory minicamps this week are the Houston Texans, Indianapolis Colts and San Francisco 49ers. The Philadelphia Eagles were the first team to skip theirs when they did so a week ago.

Teams already have been going through organized team activities, but this marks the first time that many veterans will take the field since the end of the 2020 season. That includes some players who joined new teams this offseason, including Julio Jones. Who shows up will also be something to keep an eye on, as many players could hold out amid ongoing contract negotiations. And, as always, offenses and defenses will continue installing new schemes during this time.

So what do you need to know about this week's activities? We asked our NFL Nation reporters to preview this week's minicamps and tell us the biggest thing they are watching from all 18 camps. Let's start with the Ravens, who are trying to get their new wide receivers in sync with their offense.

Jump to a team:
BAL | BUF | CAR | CHI | CIN | CLE
DEN | JAC | KC | LV | LAC | MIA
MIN | NE | NYJ | PIT | SEA | TEN

I'm watching Lamar Jackson and the new-look wide receiver group. The Ravens drafted Rashod Bateman in the first round and signed Sammy Watkins in free agency to help boost the NFL's 32nd-ranked passing attack. Bateman has missed practice time due to some muscle tightness, and Watkins skipped the first week of voluntary offseason workouts. So minicamp should allow Jackson to familiarize himself with Baltimore's biggest additions to the passing game. Last season, the Ravens completed 137 passes to wide receivers -- 18 fewer than any other team in the league. -- Jamison Hensley

How improved is Buffalo's defensive line? It was clearly a point of emphasis for the Bills after drafting defensive ends with their first two picks in this year's draft. Toss in the return of 1-technique defensive tackle Star Lotulelei, a full offseason for 2020 second-round pick AJ Epenesa and a second year under defensive line coach Eric Washington, Buffalo figures it did enough this offseason to apply the pressure on the AFC's premier offenses that it lacked last season. -- Marcel Louis-Jacques

How will QB Sam Darnold perform after a month of practicing Joe Brady's system? Participation-wise, Carolina has had close to 100% throughout OTAs, so what happens in mandatory minicamp won't be that much different from what we've seen. But how much of the system Darnold has grasped and how well he manages the offense will be important. -- David Newton

Justin Fields' progression within the offense will be the focus. Bears coach Matt Nagy already announced that veteran Andy Dalton will take the first-team reps until further notice, but Fields is penciled in as the No. 2 quarterback, ahead of Nick Foles. All eyes continue to be on the first-round pick as he learns Nagy's offense and works to improve his command of the huddle. Fields already suffered through minor growing pains in OTAs -- taking snaps under center, for example -- but his talent is undeniable. Fields will be the center of attention at minicamp and beyond. -- Jeff Dickerson

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What kind of progress will Joe Burrow continue to make? During the three OTAs available to the media, Burrow took small strides as he looks to recover from a devastating knee injury. Burrow's on-field comfort will be something to watch. Another thing to keep an eye on: Burrow's increased velocity on intermediate passes and how that translates to his deep ball. -- Ben Baby

Keep an eye on Cleveland's new-look defense. The Browns added as many as eight new defensive starters in the offseason through free agency and the draft, bolstering the talent around star pass-rusher Myles Garrett and Pro Bowl cornerback Denzel Ward. Minicamp will provide the first glimpse into the potential of this revamped unit. -- Jake Trotter

Put it on repeat: Keep an eye on the quarterbacks. The Broncos have a full-fledged, equal-snaps quarterback competition going on between Teddy Bridgewater and Drew Lock. And coach Vic Fangio has said what happens in training camp and preseason games later this summer will be the bulk of the evaluation when the team makes the decision, but he also has said that 11-on-11 work in practice matters plenty. And the Broncos will do the most 11-on-11 work of the offseason program in this mandatory minicamp. -- Jeff Legwold

How much is Trevor Lawrence progressing? He's not facing limitations as he recovers from left shoulder surgery, but he is having the normal ups and downs all rookie QBs have. The Jaguars want to see him consistently stacking good practices. Coach Urban Meyer said Lawrence's retention has been great and his execution has improved. Steady progress needs to continue. -- Michael DiRocco

Patrick Mahomes seems well ahead of schedule in rehabbing from February toe surgery, so the bigger immediate issue is who is playing where on the offensive line. The Chiefs have eight strong roster candidates on the line who weren't with the team last year. The Chiefs need to start the process of figuring out a starting five. Orlando Brown Jr. at left tackle and Joe Thuney at left guard are set. Otherwise, spots are up for grabs. -- Adam Teicher

Defense, defense, defense. Not much can be told when the guys are in shorts and helmets, right? But Gus Bradley was brought in to fix a defense that cost Las Vegas dearly in late losses to the Chiefs, Chargers and Dolphins last year, costing the Raiders a shot at the playoffs. Bradley was the architect of the Legion of Boom in Seattle. Will he make Las Vegas' secondary go boom or bust in the desert? Minicamp should give a preview. -- Paul Gutierrez

Is Justin Herbert rusty or ready? Will he have the second-year blues, or does he look strong and prepared? Based on his history, we're guessing ready, strong and prepared. He has spent his college and now his professional career adjusting to new schemes and new coaches. It should be interesting to watch him with the newest guys. -- Shelley Smith

How does Tua Tagovailoa look with his new offensive weapons? The buzz around the Dolphins' headquarters all offseason has been about building around a more comfortable, confident Tagovailoa headed into Year 2. It's true that Tagovailoa is stronger and bigger after a grueling offseason workout plan. New starting receivers William Fuller V and Jaylen Waddle add electrifying speed that should open up the offense and help Tagovailoa launch the deep ball. Everything seems to be trending the right way, but we finally get to see a real glimpse of how it'll look in true football action during minicamp. -- Cameron Wolfe

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Will Danielle Hunter show up? The Pro Bowl defensive end is the only Vikings veteran who skipped out on the entirety of OTAs while speculation over possible dissatisfaction with his contract continues to swirl. Hunter never saw the field in 2020 due to a neck injury and underwent season-ending surgery last October. All indications, from Mike Zimmer to Rick Spielman, are that Hunter is healthy and recovered. While his absence has been notable and expected for the voluntary portion of the offseason, come Tuesday, it becomes a full-on holdout if he's not at minicamp. -- Courtney Cronin

Dont'a Hightower and his plans for 2021 will be key. The veteran linebacker and longtime captain has not been attending voluntary organized team activities after opting out of the 2020 season, but players and coaches have said they look forward to his return. The question, as noted by linebackers coach Jerod Mayo, is how his body responds to a year away. For some players, including Rob Gronkowski, time away can be a boost. For others, such as Patrick Chung, it can create an additional obstacle that makes it harder to return to action. -- Mike Reiss

Minicamp will be another important marker for rookie QB Zach Wilson, who has ranged from fair to very good during scripted practices open to the media. But the coaching staff is eager to see how he performs in unscripted periods, which will test his grasp of the offense. The presumptive starter, Wilson has been getting every first-team rep, but he still hasn't had a chance to work with WR Jamison Crowder, who is staying away because of a contract squabble. Crowder will likely attend because it's mandatory, assuming he's still on the roster. -- Rich Cimini

How is Ben Roethlisberger adapting to Matt Canada's offense? The Steelers have been slowly installing Canada's scheme during OTAs, and minicamp with the full Steelers offense will be another measuring stick for the quarterback and his comfort in the new concepts. He admitted to the challenge of learning a new offense after 17 seasons in a similar system, and JuJu Smith-Schuster said he has noticed the quarterback's buy-in through the volume of questions he's asking. -- Brooke Pryor

What should we expect regarding Jamal Adams' participation? The Pro Bowl strong safety was among the Seahawks' veterans who stayed away for the start of the voluntary offseason program, but he didn't report at the start of the final week of OTAs like many others did. The Seahawks and Adams' agent have started discussions about a new contract, a source has told ESPN, but they appear to be a long ways away from getting something done. Adams would be subject to fines for skipping mandatory minicamp, though he could always show up and not practice as Bobby Wagner did early in training camp two years ago while his contract was being finalized. These three days could be an indication of what Adams plans to do if his deal isn't done by late July. -- Brady Henderson

How much will Ryan Tannehill and Julio Jones work on chemistry? The newly acquired Jones will play a key role in the Titans' passing game but is playing with a new quarterback for the first time in his 10-year career. Tannehill was able to quickly develop chemistry with A.J. Brown and some of the other receivers in 2019. If he and Jones can quickly get on the same page, it will be tremendous for the Titans' offense. -- Turron Davenport