The playoff-bound Oakland Raiders are down to their third quarterback.
McGloin made his first start since 2013 on Sunday after starter Derek Carr suffered a broken fibula last week.
The Raiders were trailing 17-0 when Cook entered the game. McGloin was 6-for-11 with just 21 passing yards when he was injured. The team announced he was questionable to return in the second half. The Raiders would clinch the AFC West title and No. 2 seed with a win. With a loss and a Kansas City Chiefs win in San Diego, Oakland would instead be a wild-card team and play next week at Houston.