LAKE FOREST, Ill. -- Chicago Bears quarterback Jay Cutler suffered a high left ankle sprain in Sunday's loss to the Detroit Lions and will not face the Baltimore Ravens, coach Marc Trestman said Monday.
Cutler's latest setback came 21 days after the quarterback returned from tearing a groin muscle in his left leg on Oct. 20 in a loss to the Washington Redskins.
"I think you all know he's got a high ankle sprain," Trestman said. "He got it rolled on. It was unrelated to the groin injury. It happened in the second quarter. They taped him up. There was no indication from the trainers there would be any further injury.
"I thought offensively he had one of his best games. I asked [the trainers] if the groin was an issue at all, [and they] didn't feel that there was. They told me even today, if he hadn't rolled up the ankle, he would have been able to play today."
With Cutler's week-to-week prognosis, the Bears will start backup quarterback Josh McCown on Sunday.
McCown entered Sunday's 21-19 loss with 2:17 left to play and led the Bears on a 10-play, 74-yard drive capped by his 11-yard touchdown pass to Brandon Marshall.
Depending on the severity of the sprain, Cutler could miss anywhere from four to six weeks. But it's worth noting that in 2012, running back Matt Forte suffered a high ankle sprain against the Green Bay Packers, missed one game, and returned to the field 18 days after the initial injury for an Oct. 1 matchup at Dallas.
Cutler suffered his injury with 2:56 left in the first half when he was hit by Detroit linebacker Stephen Tulloch as he stepped into a throw during a 12-yard completion to Alshon Jeffery. On the very next play, a 5-yard run by Forte, Cutler appeared to be in discomfort.
During a three-and-out series in the fourth quarter, Cutler short-hopped a pass Jeffery's way, and Trestman decided it was time to pull the starting quarterback. McCown entered on Chicago's very next drive.
"If you look at it closely, there was an indication that we should take Jay out," Trestman said. "It was on the last throw (of the fourth quarter as Cutler was pressured by Nick Fairley). He climbed the pocket. It was an awkward throw, and he threw the ball into the ground to Alshon."
Trestman said he's watched tape of the game twice and said he has "no regrets" for the way he handled the quarterback situation after coming under fire for not electing to insert McCown sooner.
In three games filling in for Cutler, McCown has completed 42 of 70 passes for 538 yards, four touchdowns and a passer rating of 103.1.
Trestman was reluctant to pull Cutler because he felt the quarterback was performing at a high enough level to help the team.
"I thought he looked good up until a point, and I think the ankle started getting stiffer on him and decreased his mobility and -- probably the series before, or the series or two before I went in, those series ended and he was trying to move and couldn't move," McCown said on "The Waddle & Silvy Show" on ESPN 1000. "We were evaluating it, but I'll say this over and over again, Jay Cutler on one leg -- his arm talent -- Jay on one leg is as good as a lot of guys in the NFL just from what he can do and the throws you saw him make yesterday.
"The thought as we convened on the sideline was how we can execute. We got to a point where a) it was hurting him, he wasn't moving as well, and then we knew we were getting into a two-minute situation where mobility is crucial because you're throwing it every down. It's not like there's any deception. So that's when we said if it gets to this situation why don't you take it, and it just made sense to everybody. It's a tough thing what he went through yesterday, because he's a competitor and you don't ever want to take yourself off the field."
Going into the game, the Bears removed plays requiring Cutler to move outside the pocket from the game plan, and the team attempted to protect him even more by operating out of shotgun on 12 of the team's first 13 snaps and 25 of 33 snaps in the second half.
Cutler completed 12 of 18 for 148 yards in the first half, but in the second half he hit just 3 of 12 for 59 yards, with the majority of that yardage coming on a 44-yard pass to Marshall. Cutler started the second half with incompletions on his first three passes.
"It's very tough to pull your starting quarterback out when he's throwing the ball with velocity, when he's hitting his receivers, and he's able to move in the pocket and complete a throwing motion," Trestman said. "All three of those indications confirmed with me that I should keep him in here. It's just a feel thing. It's not percentages.
"He's our starting quarterback, he's our leader. If it's in the best interest of the football team and he can move the team and not hurt himself or the team, we want him to be in there. He wants to be in there. These things come up periodically in the course of seasons and in games with your starting quarterback, and you've got to make those decisions and they're not easy ones. But there are no regrets here."
McCown owns a 2-1 record as a starter for the Bears, having thrown for 674 yards, four touchdowns and three interceptions while posting a passer rating of 82.5. Two of McCown's starts came in 2011 with a shaky offensive line and much different personnel at the skill positions than what the Bears have now.
"You saw Josh play a week ago (in an upset win over Green Bay). He played very effectively," Trestman said. "He took care of the football. He was very efficient. We hope to get the same out of him Sunday. Josh has been here working for the last eight months learning the offense, and when he's had the opportunity to play, he's played very well."