Bears lose LB Danny Trevathan to injury, but backup Nick Kwiatkoski steps up

Inside linebacker Danny Trevathan left with a gruesome elbow injury and backup Nick Kwiatkoski starred in his place during the Bears’ 20-13 victory Sunday against the Lions.

Trevathan left in the first quarter after his arm bent the wrong way under Lions quarterback Jeff Driskel’s legs and quickly went to the locker room. Coach Matt Nagy said he was unsure about the severity of the injury.

Kwiatkoski offset that loss by playing perhaps the best game of his career. He intercepted Driskel early in the third quarter to set the Bears up for a scoring drive from the Lions’ 25, sacked him in the fourth and finished second on the team with nine tackles.

Trevathan and fellow inside linebacker Roquan Smith rarely miss a snap, leaving little playing time for any of the backups. Kwiatkoski had played only 8 percent of the defensive snaps before Sunday.

When needed, though, he has come through. After Smith was a late scratch against the Vikings in Week 4, Kwiatkoski had nine tackles and a sack.

‘‘It’s just preparation,’’ he said. ‘‘As a linebacker, you plan on playing. Things happen throughout the course of a season, and you have to be ready for it.’’

As far as this being a big opportunity for him if Trevathan is out for a while, Kwiatkoski said: ‘‘It’s not the way I want it to happen. Danny’s a close friend of mine.’’

Trevathan has been the heartbeat of the Bears’ defense and leads the team with 67 tackles.

At 29, however, Trevathan’s four-year run with the Bears might be coming to an end. He will be an unrestricted free agent this spring and could command a steep contract after proving well worth his $7.7 million salary-cap hit this season.

Kwiatkoski, a fourth-round pick in 2016, also will be a free agent, but he likely will be significantly more affordable.