The former No. 1 overall draft pick was added to the 49ers' injury report Friday after feeling pain in his surgically repaired right shoulder during practice. Smith, who lost his starting job to journeyman J.T. O'Sullivan in training camp, was in street clothes for Sunday's 23-13 loss to Arizona.
The quarterback said the new injury is around the bone, near where Dr. James Andrews repaired his separated shoulder in December. The new injury could "potentially" force Smith to have another season-ending surgery, he said.
"They're trying to figure that out," Smith said. "That's the goal. Hopefully the films get down to Dr. Andrews [on Monday], and they'll talk and see what's what."
Coach Mike Nolan said he had talked with general manager Scot McCloughan over the weekend about adding another quarterback to the roster.
"We're tossing around some different names," Nolan said.
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 Andrews. 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," Nolan said in a statement. "At this time there are no specifics to the injury or a timetable."
If Smith is unable to play this season, he's almost certain to be cut by the 49ers, who would have to pay Smith more than $9 million in base salary next season. General manager Scot McCloughan said last week that Smith would be released if he wasn't San Francisco's clear-cut starter heading into next season.
Smith doesn't plan to travel to Alabama to see Dr. Andrews. He said the injury apparently occurred gradually, culminating in intense pain when Smith made a throw late in Friday's practice.
Shaun Hill, who got a hefty pay raise from the 49ers last winter after playing well in two starts following Smith's injury, is O'Sullivan's backup. The 49ers didn't have a third quarterback against the Cardinals, though running back Michael Robinson -- a former Penn State quarterback -- would be the emergency fill-in.
Smith passed for 4,679 yards with 31 interceptions and 19 touchdowns in his first three seasons with the 49ers, who selected the former Utah star with coach Mike Nolan's first draft pick.
Smith has never found a consistent NFL groove while playing for four offensive coordinators in four seasons and throwing to one of the NFL's worst collections of receivers. San Francisco's offense finished last in the NFL in 2005 and 2007.
Information from The Associated Press was used in this report.