GREEN BAY, Wis. -- The Kansas City Chiefs lost starting cornerback Phillip Gaines to a left knee injury in the first quarter of Monday night's 38-28 loss to the Green Bay Packers, and he did not return.

After the game, Chiefs coach Andy Reid said Gaines has a knee sprain and will undergo an MRI on Tuesday, according to The Kansas City Star.

The Chiefs were already short-handed at cornerback. Another starter, Sean Smith, is serving the last of his three-game NFL suspension for a violation of the league's substance-abuse policy.

The Chiefs replaced Gaines with Marcus Cooper, a former starter before being benched last season.

Even before losing Gaines, the Chiefs were having little success slowing Aaron Rodgers and the Packers. Rodgers was 6-of-9 for 74 yards and two touchdowns in the first quarter and finished 24-for-35 with 333 passing yards and five touchdowns.