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Mike Pettine's 18th season as an NFL coach will be spent with the Chicago Bears. Pettine, who most recently served as the Packers defensive coordinator, will join the Bears' staff as a senior defensive assistant, the team announced.

Pettine, 54, spent three years in Green Bay before the team elected not to renew his contract following the team's loss to Tampa Bay in the NFC Championship Game. During his time in Green Bay from 2018-20, the Packers finished 22nd, ninth, and 13th in the NFL in scoring defense, respectively. In 2020, Green Bay's defense finished seventh in the NFL in passing, 13th in rushing, tied for eighth in sacks, tied for 26th in turnovers forced, 10th in third down efficiency and eighth in red zone efficiency. Pro Bowl linebacker Za'Darius Smith had 7.5 more sacks than the next closest Packer, Rashan Gary. The Packers' other Pro Bowler on the defensive side was cornerback Jaire Alexander, who broke up a team-high 13 passes. 

The Packers' decision to part with Pettine came just days after the team's 31-26 loss to the Buccaneers. While Pettine's unit held Tampa Bay to 19 first downs and 2-of-8 on third down, the Packers could not overcome Tom Brady's three touchdown passes in the game's first 31 minutes. Green Bay's defense also allowed a 20-yard touchdown run by Leonard Fournette, as the Buccaneers stormed out to a 28-10 lead. 

With their deficit cut to five points, the Packers' defense needed to get a stop with 2:05 remaining. But two costly penalties enabled the Buccaneers to keep the ball for the remainder of the game. 

Before his time with the Packers, Pettine served as the Jets defensive coordinator when New York made consecutive AFC title game appearances in 2009-10. He spent one year as the Bills defensive coordinator before going 10-22 as head coach of the Browns from 2014-15. 

Pettine will work alongside new Bears defensive coordinator Sean Desai, who previously served as Chicago's safeties coach. A member of the Bears' staff since 2013, Desai is replacing Chuck Pagano, who retired from coaching shortly after the 2020 season came to a close. 

Last season, the Bears boasted the league's 12th-best pass defense. Chicago was also eighth in the NFL in third down efficiency and fifth in red zone efficiency. Tashaun Gipson, Chicago's starting free safety, finished the season in a tie for the team lead in interceptions. Strong safety Eddie Jackson, a Pro Bowler the previous two seasons, set career highs in tackles (82) and forced fumbles (three) during the 2020 season. The success of their backfield helped the Bears clinch a playoff berth for the second time in Matt Nagy's three seasons as coach. 

Desai, Pettine and the rest of the Bears' defensive coaching staff will have a talented group to work with in 2021. Along with Jackson, linebacker Khalil Mack and cornerback Kyle Fuller, the Bears' defense will also include linebackers Roquan Smith and Danny Trevathan. One of the NFL's biggest Pro Bowl snubs, Smith tallied 139 tackles, four sacks and two interceptions last season. Trevathan finished second on the team with 113 tackles. 

Two areas the Bears' defense will have to improve in 2021 are turnovers and pass rush. Chicago was just 25th in the NFL in forced turnovers last season. Their 35 team sacks were good for 17th in the league.