"I don't think we can say I'll be out there for Detroit," Cutler said on ESPN 1000's "Waddle and Silvy" show.
Cutler's acknowledgment backs up a report from NFL Media Insider Ian Rapoport, who was told Monday that the quarterback was unsure if he'd be able to return from his torn groin muscle by Sunday.
Cutler revealed Tuesday that he still has "hurdles" to clear and emphasized that he has to be "smart" about not pushing his body before it's ready.
Cutler won't rule out playing at 90 percent, but he's yet to reach that point in his recovery. If he's not ready to practice on Wednesday, chances are McCown will start a second consecutive game.