Brissett went down early in the second quarter after a short incompletion on first-and-goal from the 12-yard-line. The Colts QB jogged to the sideline and was checked by trainers on the sideline.
Related players: Brian Hoyer
The Colts think the injury is a sprained knee, and perhaps "MCL-ish" according to HC Frank Reich. If Brissett has to miss time, which seems like it's a possibility at this point, Hoyer would take over as the starter.