Closer look at Bills' defensive turnaround

When Mike Pettine made a lateral move last offseason, becoming the defensive coordinator for the Buffalo Bills, it gave him an opportunity to mold a defense outside the shadow of New York Jets coach Rex Ryan.

As Pettine interviews for the Cleveland Browns' head coaching job this week, it's worth circling back on the Bills' defense this season. What changed from before Pettine arrived?

Here's a look:

Personnel gains:

DL Alan Branch (unrestricted free agent)

DE Jerry Hughes (trade)

LB Manny Lawson (unrestricted free agent)

LB Kiko Alonso (second-round draft pick)

CB Nickell Robey (undrafted free agent)

S Jim Leonhard (street free agent)

Personnel losses:

DE Shawne Merriman (retired)

DE Mark Anderson (released)

DL Kyle Moore (unrestricted free agent)

DT Spencer Johnson (unrestricted free agent)

LB Kelvin Sheppard (traded)

LB Nick Barnett (released)

LB Kirk Morrison (unrestricted free agent)

S George Wilson (released)

2012 defensive ranks:

Points per game: 26th (27.2)

Yards per game: 22nd (362.9)

Rushing yards per game: 31st (145.8)

Passing yards per game: 10th (217.1)

Opposing QBR: 25th (64.6)

Completion percentage: 5th (57.1 percent))

Interceptions: 20th (12)

Sacks: Tied-18th (36)

Forced fumbles: 3rd (21)

Red zone defense: 31st (69.1 percent)

Third down defense: 31st (44 percent)

Touchdowns: 31st (48)

2013 defensive ranks:

Points per game: 20th (24.2)

Yards per game: 10th (333.4)

Rushing yards per game: 28th (128.9)

Passing yards per game: 4th (204.4)

Opposing QBR: 2nd (36.0)

Completion percentage: 1st (55.3 percent)

Interceptions: 2nd (23)

Sacks: 2nd (57)

Forced fumbles: Tied-20th (12)

Red zone defense: 6th (47.1 percent)

Third down defense: 14th (37.1 percent)

Touchdowns: 18th (38)