Over the past two weeks, the PFF analysis team has revealed our offseason grade for every NFL franchise. Several teams that earned a high mark did so because there was a specific area they were able to improve; here are the 10 units that took the biggest step forward this offseason.

1. Giants' defensive line

Old starters: DE Jason Pierre-Paul (81.1 overall grade in 2015), DE Robert Ayers (88.5), DT Jay Bromley (66.3), DT Cullen Jenkins (65.9)

New starters: DE Olivier Vernon (92.5), DE Jason Pierre-Paul (81.1), DT Damon Harrison (91.9), DT Johnathan Hankins (77.5)

The Giants take the top spot after they added two of the best free agents available (regardless of position). In 2015, New York tried 14 different players on the defensive line, with no player receiving more than 750 snaps. To remedy that shuffle, they signed former Dolphin Olivier Vernon, who averaged one sack, three hits, and three hurries over the second half of last season. They also inked former Jets NT Damon Harrison, who led all defensive tackles in run-stop percentage each of the last three seasons. When you throw in the return of Jonathan Hankins, who only played the first half of 2015, and Jason Pierre-Paul, who only played in the second half of the season, and the Giants—on paper—now have one of the top defensive lines in the NFL.

2. Bears' inside linebackers

Old starters: John Timu (49.3), Christian Jones (65.2)

New starters: Jerrell Freeman (90.6), Danny Trevathan (86.6)

For several years, the Bears didn’t have to worry about their linebacker position because they had Brian Urlacher and Lance Briggs. Prior to this offseason, however, they had failed to find adequate replacements. Throughout the 2015 season, the Bears tried five different players at ILB, with all five of them receiving below-average grades. This year’s linebacker free-agent class wasn’t very deep, but the Bears made the most of it by adding both of the best linebackers available; both Jerrell Freeman from the Colts and Danny Trevathan from the Broncos were in the top five for run-stop percentage last season. What Chicago has done not just at inside linebacker, but the entire front-seven, to transition to a 3-4 defense has been very impressive.

3. Raiders' defensive backs

Old starters: CB David Amerson (83.4), CB T.J. Carrie (46.3), FS Charles Woodson (79.0), SS Taylor Mays (64.6)

New starters: CB Sean Smith (83.8), CB David Amerson (83.4), FS Reggie Nelson (84.2), SS Karl Joseph (rookie)

The Raiders' defensive backfield had a complete makeover over the course of the offseason. First they brought in one of the biggest names in free agency, Sean Smith. In his seven-year career with the Chiefs, Smith has never allowed a catch rate above 59 percent. In six of his seven career years, he’s recorded at least eight passes defensed. While Reggie Nelson is only a quick fix at safety, he notched eight interceptions last year, tied for the most among all defensive backs in 2015. Finally, in the draft, they added Karl Joseph out of West Virginia, who had more interceptions (five) than catches allowed (four) in his limited playing time last season.

4. Texans' interior offensive line

Old starters: LG Xavier Su’a-Filo (52.0), C Ben Jones (69.4), RG Brandon Brooks (66.7)

New starters: LG Jeff Allen (85.5), C Nick Martin (rookie), RG Tony Bergstrom (76.4)

The interior of the Texans' offensive line used to be a strength after Brandon Brooks and Ben Jones were drafted in 2012 to play guard around center Chris Myers. In 2015, though, the Texans were without Myers, and the line didn’t play nearly as well. Both Brooks and Jones left via free agency, but the Texans did a good job in replacing both, as well as finding a new guard. Former Chief Jeff Allen earned the sixth-highest run-blocking grade among guards last season, and didn’t allow a sack or hit all year. Tony Bergstrom’s playing time has been limited in his career, but in 254 snaps in 2015, he didn’t allow a sack or hit, either, and was an above-average run-blocker. Finally, they added Nick Martin in the draft; the former Notre Dame O-lineman is known for his run-blocking, but also didn’t allow a sack or hit in 2015. While it might take time for them to develop chemistry together, the interior line should become a strength for Houston again soon.

5. Buccaneers' cornerbacks

Old starters: Sterling Moore (66.8), Jude Adjei-Barimah (48.1), Johnthan Banks (42.9)

New starters: Brent Grimes (74.8), Vernon Hargreaves (rookie)

Throughout the 2015 season, Tampa Bay had players rotating in and out of the starting lineup at their outside cornerback spots, with no combination of players working well for them. That should change in 2016 after adding two new outside CBs this offseason. First they brought in former Dolphin Brent Grimes, who was one of seven cornerbacks in 2015 with both four or more interceptions and seven or more passes defended. In the draft they added Vernon Hargreaves to play opposite of Grimes. For Florida in 2014, Hargreaves allowed an NFL passer rating of 41.6 when targeted, and he played at roughly the same level in 2015, with a passer rating allowed of 49.0. The Buccaneers should have more consistency and better play out of their cornerbacks this upcoming season.

6. Cowboys' running backs

End-of-season depth chart: Darren McFadden (68.8), Robert Turbin (65.6), Rod Smith (60.3)

New projected depth chart: Ezekiel Elliott (rookie), Alfred Morris (69.7), Darren McFadden (68.8), Lance Dunbar (71.1)

There was plenty of running back movement in free agency, as well as a lot of running backs drafted who can make an impact this year, but no team improved more at the position than Dallas. The Cowboys' biggest headline of the offseason was the addition of Ezekiel Elliott. The former Buckeye recorded 1,050 yards after contact alone, fourth-best for college running backs last year. Adding Alfred Morris from Washington in free agency didn’t get as much attention, partially due to his down year in 2015, but in two of his four years in the league, he’s been among the top five running backs in forced missed tackles recorded. Throw in the return of Lance Dunbar, who was leading the league in yards per route run for running backs before his injury, and incumbent starter Darren McFadden might not have a role in the offense in 2016.

7. Saints' defensive tackles

Old interior rushers: Kevin Williams (77.7), Tyeler Davison (59.2)

New interior rushers: Nick Fairley (82.0), Sheldon Rankins (rookie)

Year after year, the Saints have consistently had one of the worst pass-rushes in the NFL. This past season, Cameron Jordan had a great campaign, but no other player in the front-seven had both a positive pass-rush grade and at least one sack. That should change in 2016, thanks to the additions New Orleans made at defensive tackle. They added Nick Fairley from the Rams, who has earned an above-average pass-rush grade in each year of his career, thanks to his ability to consistently bring pressure. They also brought in Sheldon Rankins via the draft. The former Louisville Cardinal recorded a 9.3 pass-rushing productivity, fifth-best for 3-4 defensive ends in college last year. The new pass-rushing duo should make things easier for the entire Saints' defense.

8. Vikings' offensive linemen

Old starters: LG Brandon Fusco (61.6), RT T.J. Clemmings (36.8)

New Starters: LG Alex Boone (65.0), RT Andre Smith (39.6)

Just by looking at 2015 grades, the Minnesota line doesn’t look like it improved much. However, if everyone returns to playing their best football, the Vikings could own one of the best offensive lines in football this season (when you include both starters and backups). Former 49er Alex Boone has graded above-average in each year of his career, and at his best, was a top-three guard in the NFL. He is projected to play left guard, which moves Brandon Fusco back to right guard. 2013 was Fusco’s last full year at right guard, and he was a top-five run blocker that season. While Andre Smith had a down year in 2015 with Cincinnati, at his best he was a first-team PFF All-Pro. Throw in the return of John Sullivan and Phil Loadholt, and the line has the potential to be special.

9. Jaguars' cornerbacks

Old starters: Davon House (73.1), Dwayne Gratz (51.3), Aaron Colvin (74.6)

New starters: Davon House (73.1), Jalen Ramsey (rookie), Prince Amukamara (78.9)

The Jaguars spent the offseason improving at several positions, earning an “A” grade from PFF's analysis team. The position group that improved the most, though, was cornerback. Year after year, Prince Amukamara has graded as an above-average NFL CB. In 2015, he averaged 1.04 yards per coverage snap, tied with Darrelle Revis for 15th-best in the league. Then, in the draft, Jacksonville added former Florida State Seminole Jalen Ramsey, whose 16 stops in the passing game were tied for fourth-best in the FBS last year. They will join Davon House, who had 13 passes defenses in 2015, tied for fifth-best in the league. Simply put, the Jaguars no longer have a weakness at the cornerback position.

10. Browns' wide receivers

Previous players: Travis Benjamin (69.8), Brian Hartline (72.1), Dwayne Bowe (60.6)

New players: Corey Coleman (rookie), Rashard Higgins (rookie), Jordan Payton (rookie), Ricardo Louis (rookie)

There were very few good wide receivers in free agency, and the draft class wasn’t as strong as previous years, so if a team wanted to revamp their receiving corps, it was going to be very difficult to do so. Despite that, the Browns found a way by drafting four wide receivers who could all see significant playing time this year. Their two most promising receivers were Corey Coleman and Rashard Higgins, who finished third and fifth, respectively, in yards per route run in 2015. While it might take a year or two for the receivers to develop, it will be sooner rather than later before they become a strong unit.