CHICAGO -- Bears quarterback Jay Cutler left Sunday's 21-19 loss to the Detroit Lions late in the fourth quarter with what the team is calling a sprained left ankle.

Initial tests, done at Soldier Field, came back negative, according to Bears coach Marc Trestman. But the team won't know the full extent of the injury until Monday.

Cutler returned to action Sunday exactly 21 days after tearing a muscle in his left groin on Oct. 20 against the Washington Redskins. Cutler and Trestman said the groin never gave the quarterback any discomfort in Sunday's game, although it appeared to be the cause of pain on multiple occasions throughout the contest.

Cutler said he sprained the ankle just before halftime. He left the game with 2:17 remaining.

"I just didn't feel I could make some of the throws I wanted to make and move around, couldn't be as mobile," Cutler said. "[The groin] held up OK. It's all in the same leg, so I think that was a problem. We taped it up and it was stiff. But I felt like I could go as long as I kept it moving."

After Cutler injured the ankle, he spoke on the sideline with backup Josh McCown and Trestman in between every series on offense as the trio tried to remain in constant communication about Cutler's ability to continue to play.

Throughout all the dialogue, Cutler "never talked about the groin at all," according to Trestman, who added that "there was never a sense at all that he was impeded by his groin today."

Bears receiver Brandon Marshall actually said that Cutler "probably from the second drive [of the game], had all kinds of things going on him from his waist down," and called the quarterback "a soldier."

McCown entered the game just before the two-minute warning and led the Bears to a late touchdown on an 11-yard scoring strike to Marshall. Trestman said the decision to insert McCown came as the result of him wanting a quarterback with enough mobility to execute the two-minute drill.