"I think it was just fatigue in his quad, and it tightened up on him," said Sherman, who wasn't sure if Walker would be ready for Tuesday's full-squad practices.
The most serious injury belongs to defensive end Tyrone Rogers, a late addition to the training camp roster who is in the hunt for a backup position. The former Cleveland Brown suffered a sprained medial-collateral ligament in a knee. Sherman said Rogers is out indefinitely.
Quarterback Brett Favre earned a day off to rest his arm after throwing 27 passes — with 21 completions covering 249 yards and five touchdowns — on Saturday night.
Starters remaining out of action are tight end Bubba Franks (chest), center Mike Flanagan (knee), left guard Mike Wahle (knee) and nose tackle Grady Jackson (knee). Key reserves still out of action are quarterback Craig Nall (hamstring), cornerback Joey Thomas (knee), defensive tackle Donnell Washington (foot) and defensive end Chukie Nwokorie (hamstring).
Monday's special-teams practice runs from 8:45-9:30 a.m., and two-a-days return Tuesday with 8:45 a.m. and 2:15 p.m. sessions.