The Carolina Panthers acquired defensive end Jared Allen from the Chicago Bears on Monday in exchange for a 2016 sixth-round draft pick.

“We had some depth at the linebacker position,” Bears General Manager Ryan Pace said in a news release. “... Whether it is acquiring additional picks or signing players, we will continue to be aggressive in finding ways to improve our football team.”

The Panthers made the move after their top pass rusher, Charles Johnson, went down with a hamstring injury in Sunday’s 27-22 win over the Saints. Johnson has already been ruled out of Carolina’s Week 4 game vs. Tampa Bay.

The Panthers lost their other top pass rusher, Greg Hardy, this past offseason when he signed with the Dallas Cowboys as a free agent.

Allen, 33, has 134 career sacks — more than any active player in the NFL — during his 12 seasons, which included six seasons with the Vikings (2008-13) during which he started every game and recorded 85.5 sacks. But his production has dropped off sharply since he joined the Bears last season and began playing in a 3-4 defense. He’ll play in a more familiar 4-3 set with Carolina.

• The NFL vice president of officiating said referee Ed Hochuli insists he never told Carolina quarterback Cam Newton that he “wasn’t old enough” to get a personal foul call during Sunday’s game against New Orleans. Newton said he felt a personal foul should have been called on Saints defensive tackle Tyeler Davison for a hit out of bounds.

Pittsburgh

Steelers coach Mike Tomlin confirmed quarterback Ben Roethlisberger’s knee injury but offered little beyond that. Tomlin said Roethlisberger will miss “a number of weeks” after spraining his medial collateral ligament (MCL) in Sunday’s 12-6 victory over the Rams. “I don’t have great detail about what that length of time might look like or might be, to be quite honest with you,” Tomlin said. “I know he’s out this week.”

Etc.

• Browns quarterback Josh McCown suffered a cut on his right hand in Sunday’s loss to Oakland.

• Jets guard Willie Colon will be sidelined at least one game with a sprained knee.