Trestman said Cutler's time frame for recovery remains week to week.
Cutler left the locker room still wearing a hard cast on his left leg after Sunday's overtime win against the Baltimore Ravens, and on Monday, the quarterback had the cast taken off to get the ankle re-evaluated before another cast was put on.
"Jay would remain week to week," Trestman said. "I would rule Jay out for Sunday."
When Cutler originally sustained the injury Nov. 10, he expected to return by the team's Dec. 1 game at Minnesota, "but now, I don't know," the quarterback said Monday during "The Jay Cutler Show" on ESPN 1000. "We're taking the cast off periodically, just kind of checking to see where I'm at. We'll see again later this week, then early next week where it's at."
Cutler alluded to the injury possibly being more significant than what was originally diagnosed.
"There are a couple of ligaments that we're a little worried about that's different than the normal high ankle sprain," he said. "There are a few other things involved. If I just had a normal high ankle sprain, I wouldn't be in a cast. [A cast] helps it scar up and stuff, but the normal high ankle sprain isn't really a concern at this point."
Filling in for Cutler against the Ravens, backup quarterback Josh McCown improved to 2-0 as a starter, throwing for 216 yards and a touchdown with a passer rating of 92.9.
McCown completed 2 of 3 passes for 57 yards -- including a 43-yard strike to tight end Martellus Bennett -- during the game-winning drive in overtime.
McCown has played well in Cutler's absence, but none of that goes into consideration as the staff continues to evaluate a possible return for Cutler.
"Jay is the quarterback of our football team, and Josh is our backup quarterback," Trestman said. "The three of us all know that. That hasn't changed, and it's not gonna change."
McCown has played parts of two other games as well, and has thrown for 754 yards with five touchdowns, no interceptions and a passer rating of 100.0.
"Josh is a talented player, and he plays within himself," Trestman said. "He knows what his strengths are, and he plays to his strengths. He tries to keep things simple in terms of how he does things. He's got great work ethic. He's detail-oriented, just like Jay is -- and quarterbacks who are efficient playing the game, they're very detail-oriented. Josh is one of those guys."
Cutler suffered the ankle injury against the Detroit Lions on Nov. 10, just 21 days after tearing a groin muscle in the same leg during a loss at Washington.
"I'm pretty frustrated. It's hard being out like this," Cutler said. "I'm glad the guys are winning. I'm glad Josh is playing at a high level. That makes it easier. But I get paid to play football. Whenever I can't play and help the guys, it's difficult."
Chicago plays its next two contests on artificial turf at St. Louis on Sunday, followed by a trip to Minnesota.
Cutler hasn't played in a full game since Chicago's win over the New York Giants on Oct. 10.
"As I've said many times, we're not gonna put a player out there if there's any sense that he's gonna reinjure himself," Trestman said. "I don't ever make those decisions. I make the final decision certainly, but I listen to the doctors and the trainers.
"It's ultimately my responsibility to play a player. But we're gonna do what I feel is the best thing to do -- that's to listen to what the medical people say, and then work those players out with coaches, see if they're at full strength and that they can do all the things necessary to explode in a game. That's how we're gonna approach it. We're gonna be very, very careful."