SAN FRANCISCO -- San Francisco quarterback Alex Smith separated his right shoulder on the third play of Sunday's game against the Seattle Seahawks and the 49ers don't know when he'll be able to return.
Smith, who had taken every snap for the 49ers the past two seasons, was driven hard to the ground on a sack by Seattle's Rocky Bernard on San Francisco's first drive. He didn't return to the game.
"It's frustrating," Smith said. "I came out here to win the game. I prepared all week and I couldn't be out there. It's frustrating."
Smith didn't return, and coach Mike Nolan said it was unlikely he would be able to play next week against Baltimore. Smith was expected to undergo an MRI today to determine the degree of separation in the shoulder.
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"He's so tough. He is truly the toughest kid I've been around," backup Trent Dilfer said. "He's disappointed, obviously. He takes great pride as he should in availability is your best ability. When you can't go, and I've been there, it's devastating."
Dilfer struggled in the relief role, going 13-of-33 for 128 yards and two interceptions. He was sacked five times and could only lead San Francisco to one field goal in the 23-3 loss to Seattle.
"He certainly wasn't good enough for us to win the game," Nolan said. "But he's an outstanding leader. I don't lack confidence in him."
Next up for the 49ers is a game next week against the Baltimore Ravens, a team that has one of the best defenses in the league.
Dilfer played for the Ravens in 2000, helping them win the Super Bowl.
MOMENTUM SHIFT -- The 49ers weren't able to capitalize on two big special teams plays.
With San Francisco's offense sputtering in the second quarter, the 49ers defense forced a punt. Keith Lewis came in off the left edge, and while being blocked by Jordan Babineaux, reached out his right arm and blocked Ryan Plackemeier's kick. It was Lewis' third block in the NFL.
The ball traveled only 6 yards before going out of bounds, setting San Francisco up at the Seattle 48, trailing just 3-0. The 49ers threw two straight incompletions and allowed a sack before punting the ball back to the Seahawks.
Trailing 13-0 at the half, the 49ers caught Seattle by surprise by pulling off a successful onsides kick to open the second half.
Joe Nedney, who had five successful onsides kicks the past two seasons, pulled off a perfect one that was recovered by Delanie Walker at the San Francisco 46. But before the 49ers could enjoy the play, Dilfer threw an interception to Marcus Trufant that gave the Seahawks the ball right back.
Seattle drove down the field and scored on a 14-yard touchdown pass from Matt Hasselbeck to Marcus Pollard to make it 20-0.
NO ACTION FOR JACKSON -- Receiver Darrell Jackson had a quiet game against his former team, catching just three passes for 38 yards. Jackson had been hoping for a better performance in his first game against the Seahawks since they traded him to the 49ers for a fourth-round pick in late April.