Gaines, 24, left in the first quarter of Monday night’s 38–28 loss to the Green Bay Packers. After the game, Chiefs head coach Andy Reid said the former third round pick’s injury was a knee sprain, but an MRI later revealed the ACL tear.
In three games this season, Gaines has six combined tackles.
The Chiefs (1–2) travel to Cincinnati to face the Bengals (3–0) on Sunday.
- Kayla Lombardo