The Buffalo Bills' backfield is banged up at the moment.

LeSean McCoy has been battling a hamstring all season, and now backup Karlos Williams has an injury issue of his own. Bills general manager Doug Whaley told WGR 550 in Buffalo on Tuesday that Williams suffered a concussion Sunday in the team's loss to the New York Giants.

"We're going to see how he proceeds throughout the week. With the concussion you just don't know how they're going to respond," Whaley told WGR, per the Bills' team website.

The rookie running back will now enter the concussion protocol, and his status for Buffalo's Week 5 matchup with the Tennessee Titans is up in the air. Williams was a standout in the Bills' Week 3 win over the Miami Dolphins, rushing for 110 yards on just nine carries. He was bottled up for the most part against the Giants with just 40 yards on 18 carries, but he did catch three passes for 30 yards, including a touchdown.

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