Kansas City Chiefs running back Jamaal Charles is doubtful to play Sunday against the San Diego Chargers as he continues to recover from ACL surgery, head coach Andy Reid said Friday.

"He's probably not going to play," Reid conceded to reporters.

Reports on Charles' progress were positive early in the summer, but have taken on a decidedly pessimistic tone in recent days. It's unclear if the veteran suffered a setback in his rehab or if he is simply not as far along as it seemed.

With Charles sidelined, the Chiefs are expected to deploy a combination of Spencer Ware and Charcandrick West in their backfield. Ware looked like the superior player in the preseason, but it is West who is listed atop the team's depth chart at the moment.