The deal ends a disappointing stay in Chicago for Allen, who signed a four-year, $32 million deal before the 2014 season. After recording a career-low 5.5 sacks last year, Allen had no sacks and just five tackles in the Bears' new 3-4 defense this season.

With Johnson on the shelf indefinitely, the unbeaten Panthers obviously felt they had to make a bold move. After beginning the season with five sacks of Jaguars quarterback Blake Bortles, they've recorded just one in each of the past two weeks. And while the Saints made a concerted effort to get the ball out quickly on Sunday, a legitimate Super Bowl contender wouldn't let Luke McCown complete 27 of his first 30 passes in his first start since 2011.

Pending the Monday Night game, the Panthers are seventh in the NFL with seven sacks through three weeks. According to rankings by Pro Football Focus, Carolina's pass rush is currently No. 21.

The Panthers didn't add a defensive end in free agency or the draft, hoping they could again fill the position by committee. After Frank Alexander tore his Achilles in the preseason, Rivera said Kony Ealy "took the bull by the horns" to earn a starting spot across from Johnson. In three games, Ealy has four tackles and no sacks while playing 59 percent of possible snaps. Mario Addison, who had two sacks in Week 1, will remain in a situational role while Wes Horton plays on more obvious run downs.

The Bears paid Allen an $11.5 million roster bonus earlier this year, and because his base salary is $1 million, the Panthers owe him less than $900,000 the rest of the season. The final two years on his contract are non-guaranteed at $8.5 million in 2016 and $8 million in 2017.

The deal is the second in the past month for Dave Gettleman, who didn't trade for a player during his first two seasons as Panthers' general manager. Four weeks ago, he dealt a conditional late round pick to Seattle for receiver Kevin Norwood.