Coach Marc Trestman wouldn't say how the injury happened on Wednesday, other than Bushrod fell and it was an accident. He said he wasn't sure how severe the injury is.
If Bushrod can't play, Michael Ola could move to left tackle after filling in for Slauson.
Defensive tackle Jeremiah Ratliff (concussion) sat out Thursday. He still has to pass some tests to be cleared.
AP NFL websites: http://www.pro32.ap.org and http://www.twitter.com/AP-NFL