The Bills defense played a major role in the team’s playoff run last season.
They allowed just one touchdown and seven interceptions in 14 games.
The Bills have one of the league’s best defenses in 2015, ranking 11th in DVOA.
The defense finished tied for 10th in the NFL in points allowed per game (20.7), third in rushing defense DVOA (5.1) and fourth in total defense DVOTA (24.5).
The Bills will try to improve on that group of results this season with new defensive coordinator Keith Butler and a slew of new players coming back from injuries.
Here are some key areas of concern.
The secondary The Bills had two starting safeties return from last year’s season-ending injuries in Jairus Byrd and Jairon Robertson.
That group combined for a whopping four interceptions, including two on a pair of deep passes from the outside.
The unit struggled in the red zone, allowing a league-low 4.4 yards per attempt.
While the secondary will need to improve against the run, there is still enough talent to be a good one.
Tyrod Taylor and rookie cornerback Stephon Gilmore will be the primary targets, but it’s not as if they are the only ones.
Veteran cornerback Brent Grimes and rookie receiver Davante Adams could also contribute.
Cornerback Stephon Rollins and safety Malcolm Butler are also expected to contribute, though Rollins missed the start of training camp with a groin injury.
A big addition in free agency is cornerback Dee Milliner, who is expected to be the top corner on the team.
The team signed former Denver Bronco Aqib Talib, who has experience playing opposite of Talib in Denver.
Talib is a physical cornerback with a big frame and good size, but he has struggled to live up to expectations this season.
If Talib can make a leap forward, the Bills secondary could be even better.
Safety Marcus Gilchrist has been the most productive of the group, though he could be lost to the NFL.
Safety Lorenzo Alexander was the team, as well, and while he is expected back after missing the first two weeks of the season due to injury, he has played sparingly this season and has yet to record a single tackle.
Outside of the cornerbacks, the secondary struggled with the pass, allowing just 13.7 points per game.
The safety corps also struggled.
Safety Jamal Adams missed the entire preseason and is expected out after two games.
Cornerbacks Brandon Boykin and Robert Blanton are expected to play a large role this season, but there is no question about their importance.
Both are athletic safeties with solid ball skills and could give the Bills an edge.
Linebacker Lorenzo Alexander and cornerback Stepon Rollins are both expected to make an impact in the secondary.
Both played well for Buffalo last season, earning first-team All-Pro honors.
The front Seven pieces The Bills front seven was among the league leaders last season in total yards per game and rush defense DVVA, but their overall performance was disappointing.
The group finished fourth in defensive DVOA, 13th in pass defense DVPA and 25th in passing DVOA and was the only unit to allow a negative yards per play differential.
The offense The Bills offense was inconsistent last season and the team will look to make some significant changes this season to help it get back to the playoffs.
Running back C.J. Anderson, who missed the first five games of the year with an ACL injury, was the most consistent back in Buffalo last year.
The addition of veteran running back Tyrod Thompson, along with rookie tailback D’Onta Foreman, will help the Bills offense get back on track.
Running backs coach Chris Ballard said that Thompson is the “go-to guy” when it comes to running the ball, and he is due to make his first career start in a Buffalo uniform.
Thompson averaged 6.7 yards per carry in 2015 and was second on the Bills in rushing yards, behind only Foreman.
The running back position is a weakness for the Bills and could be a major concern heading into the season.
Rookie quarterback Tyrod Brissett, who struggled to establish a consistent rhythm last season due in part to his injuries, will be expected to take over the offense in Buffalo.
Running the ball is an area of concern for the offense, though, as it ranked 25th overall in rushing DVOA last season despite averaging 7.1 yards per rush.
With the offensive line having a lot of new faces, the front seven could struggle to stay healthy.
The defensive front seven should help the unit, but the defense will need a major boost if the Bills want to reach the playoffs in 2015.
The special teams unit While the Bills did not have a special teams standout last season (Byrd), they did have some decent performers.
Rookie tight end Marcell Dareus had the most receiving yards (1,000) and the most kickoffs (37) of any tight end last season after