Fearing he has the same injury that cut short his 2007 season -- only this time to his non-throwing shoulder -- Smith said after Sunday's 23-20 loss to Carolina that he planned to fly to London with the team and get an MRI there. His playing status for next week's game against Denver is uncertain.
"It's definitely the AC, I think. It's very similar," Smith said, referring to the acromioclavicular joint that's sometimes called a separated shoulder. "But I don't know to what I extent. There's not really much to say right now."
Smith, who was injured on a third-quarter sack, said X-rays were negative, but he was wearing a black sling after the game. His injury is complicated by San Francisco's travel schedule. The team was to fly directly from Charlotte to London after Sunday's game.
"As of right now, we'll have to wait and get an MRI," coach Mike Singletary said. "We'll see how that works out and go from there."
Entering the game with a league-high nine interceptions, Smith completed nine of 19 passes for 129 yards, one touchdown and no turnovers before a mix-up on protection allowed Johnson to come in and get Smith on the blind side, driving his shoulder into the turf.
Then came the familiar pain from 2007.
"You come down with all his body weight on that one point," Smith said. "I knew as soon as I landed on it. Same feeling, same pain."
Smith could only watch as David Carr replaced him with the game tied at 10 and threw a crucial interception with just over a minute left that set up John Kasay's game-winning 37-yard field goal with 39 seconds left.
Carr completed just 5 of 13 passes for 67 yards, and with the 49ers (1-6) in desperation mode, Smith is hopeful he might be able to return quickly if the injury isn't too serious.
"The left hand doesn't do much," Smith said. "It doesn't really affect throwing. If you can take snaps and hand the ball off, I think you can still be pretty functional."