ALAMEDA, Calif. -- Starting right tackle Menelik Watson has not been cleared yet to play in Sunday's game in San Diego after suffering a concussion during last week's loss to the Denver Broncos.

Watson did not practice on Wednesday and instead was limited to doing conditioning work on an adjacent field along with several other injured Oakland players. Khalif Barnes is Watson's back-up but has been playing left guard while rookie Gabe Jackson is sidelined with a knee injury.

Matt McCants, a second-year player who started three games for the Raiders in 2013, took all the reps at right tackle with Oakland's first-team offense.

Backup fullback Jamize Olawale (shoulder) was also absent Wednesday, forcing the Raiders to use Spencer Hadley -- a rookie linebacker on the practice squad -- on offense in practice.

The situation isn't much better on defense.

Cornerback DJ Hayden joined the group of injured players working out separately after injuring his groin against the Broncos. With Carlos Rogers also out due to a knee injury and safeties Tyvon Branch and Usama Young done for the year, Oakland's secondary is getting thin.