NFL roster rankings for all 32 teams for 2021: Strengths, weaknesses and X factors for every team's starting lineup

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Super Bowl-winning franchises rarely return their entire starting lineup the following season, but that's exactly what the Tampa Bay Buccaneers have done ahead of the 2021 NFL campaign. It's no surprise that they're one of the favorites to again bring home the Lombardi Trophy this season, but how much have the other 31 NFL teams done over the past few months to knock the Bucs off their pedestal?

With the 2021 draft and free agency behind us, we're breaking down each team's roster using the PFF database, with an eye toward the projected starters. We looked at both the PFF grades from the 2020 season — a number included for every projected starter — and a more comprehensive look at each player's career using both PFF grades and statistics.

• PFF grades of 90.0-plus categorize as elite, 80.0-89.9 are good/high quality, 70.0-79.9 fall under average and 69.9 or lower are considered below average.
• For rookies and players not active (or barely active) in 2020, we used college grades or NFL grades from earlier seasons. NFL grades from 2019 or earlier are marked with (*), college grades from 2020 are marked with (**), and college grades from 2019 or earlier are marked with (***).

Here's how the 32 rosters stack up heading into this season, complete with each lineup's biggest strengths, weaknesses and X factors.

ARZ | ATL | BLT | BUF | CAR | CIN | CHI | CLE | DEN | DAL | DET | GB | HOU | IND | JAX | KC | LVR | LAC | LAR | MIA | MIN | NE | NO | NYG | NYJ | PHI | PIT | SF | SEA | TB | TEN | WFT

1. TAMPA BAY BUCCANEERS

Biggest strength: Tom Brady only had one wide receiver or tight end clear a 70.0 receiving grade in his final season with New England in 2019, and Julian Edelman (72.4) barely met the threshold. But in 2020, Tampa Bay had six different wide receivers and tight ends record at least a 75.0 receiving grade, including O.J. Howard in limited action. It's one of the deepest receiving corps in the NFL, extending beyond those six to include promising young players such as Scotty Miller, Tyler Johnson and rookie Jaelon Darden.

Biggest weakness: Running back Leonard Fournette‘s stretch of success last postseason doesn't change the fact that 19.1% of his carries have gone for first downs or touchdowns since entering the NFL (third lowest among 30 running backs with 500-plus attempts). Ronald Jones II was an effective runner last season (84.7 rushing grade), but he can't be relied upon on passing downs. Jones tallied just 165 receiving yards on 41 targets in 2020. It's difficult to find a true weakness on this roster, but the running back position is the closest thing to it in the starting lineup.

X factor for 2021: Linebacker Devin White recorded an 83.5 coverage grade across his final five games of the 2020 season, three of which were playoff games. White also came up with 10 quarterback pressures and four sacks over that stretch. The next step in his development is to play at that level with more consistency, like his teammate Lavonte David has done for years. There's no denying that White's speed in the middle of Tampa Bay's defense can be a game-changer.

2021 Buccaneers

X factor for 2021: Kemoko Turay got out to a tremendous start to the 2019 season, recording 14 pressures on 61 pass-rushing snaps before an ankle injury prematurely ended his year. That same ankle injury lingered into 2020. As a result, Turay was only able to play 104 snaps this past season without the same kind of explosion he showed prior to the injury. He'll have an opportunity to take on a larger role in 2021 due to the losses of Justin Houston and Denico Autry.

Biggest weakness: Seattle struggled to generate any kind of consistent pass rush without the aid of the blitz in 2020. Safety Jamal Adams was tied for the team lead in pressures (26) through 14 weeks of the regular season. The offseason additions of Kerry Hyder Jr. and Aldon Smith (who once again has off-field questions hanging over his head) aren't likely enough to flip that switch. The Seahawks need young players such as Alton Robinson and L.J. Collier to come on strong this season.

X factor for 2021: Ahkello Witherspoon has bounced between truly impressive performances and dismal showings across his first four seasons in San Francisco. He earned a 73.7 coverage grade as a rookie in 2017 only to see that grade drop to 39.8 the following season. He was playing well to start the 2019 season only to lose his job late in the year while fighting back from a foot injury. Given Seattle's cornerback depth, the decision to sign Witherspoon to a one-year deal in the hopes of a healthy and productive season seems like a worthwhile risk.

Biggest weakness: The nicest thing that you can say about the Steelers' offensive line is that it has potential. Pittsburgh will be relying heavily on inexperience up front. Chukwuma Okorafor, Kevin Dotson, Kendrick Green and Zach Banner have played a combined 248 NFL snaps at the positions they're projected to start the season at. David DeCastro‘s recent release following a career-low PFF grade in 2020 and the signing of Trai Turner just add more moving parts for first-year offensive line coach Adrian Klemm. Multiple players will have to develop quickly for this unit not to stand out as a weakness this season.

X factor for 2021: The offseason losses of Steven Nelson and Mike Hilton at cornerback place more pressure on Cameron Sutton to be an integral part of this secondary this season. Sutton has ranked in the 94th percentile among all cornerbacks since 2019 in coverage grade on a per-snap basis, though much of that grade stems from his work in the slot as the fourth cornerback in dime packages. Suddenly, he's the No. 2 behind Joe Haden and the favorite to start the season on the boundary.

Biggest weakness: The receiving depth behind Michael Thomas will likely mean that he will see 2019 levels of target share. In that 2019 season, Thomas single-handedly recorded over 50% of the team's receptions and receiving yards coming from the wide receiver and tight end positions — a statistical outlier when comparing across the remainder of the NFL. Secondary options headlined by Tre'Quan Smith, Marquez Callaway and Adam Trautman mean a similar performance may be necessary this season.

X factor for 2021: Jameis Winston passed for 33 touchdowns and 30 interceptions the last time he had a starting quarterback job. That's about as X factor as it gets. It will be interesting to see not only how coach Sean Payton integrates both Winston and Taysom Hill into this offense but also how the passing offense evolves with Winston as the projected starter. Winston led all qualifying passers in average depth of target (10.8 yards downfield) in his five seasons with the Buccaneers. Over that same stretch, the Saints' offense ranked 32nd in aDOT (7.5 yards).