SANTA CLARA, Calif. -- The San Francisco 49ers added quarterback Alex Smith to their injury report Saturday, listing him as doubtful for Sunday's game against Arizona with another problem in his surgically repaired right shoulder.
Shaun Hill will be the backup against the Cardinals.
The 49ers didn't specify what was wrong with Smith, only saying the injury occurred without contact during practice Friday. Smith, the former No. 1 overall draft pick, was expected to back up J.T. O'Sullivan, who beat out Smith for the starting job in training camp.
Smith woke up Saturday morning in "severe pain" and an MRI showed that a piece of bone broke off the shoulder at a point where it was surgically repaired in December, a team source with knowledge of the diagnosis told ESPN's Chris Mortensen.
The team will await what they hope is a more conclusive exam from Dr. James Andrews, the Birmingham orthopedic specialist who performed the surgery on Smith in December. Smith had experienced mild soreness in the shoulder during the week but not significant enough to raise serious concern.
"He will be consulting with his surgeon in Birmingham for treatment recommendations," coach Mike Nolan said in a statement. "At this time there are no specifics to the injury or a timetable."
Andrews performed surgery on Smith in Alabama in December, about 2½ months after Smith's shoulder was separated on a sack by Seattle's Rocky Bernard. Smith attempted to play through the injury but struggled and eventually went on injured reserve in mid-November while trading public jabs with Nolan about the severity of his injury.
Running back Michael Robinson, the former Penn State quarterback, is likely to be the No. 3 quarterback.
Information from The Associated Press was used in this report.