A year ago, the 49ers' Aldon Smith would have watched such a play from the sideline. He was a pass-rush specialist at the time.
Smith's current role as an every-down outside linebacker required him to defend that Vikings play Friday night. Smith chased running back Toby Gerhart, only to trip over teammate Donte Whitner. Smith landed hard on his right side, suffering a bruised hip.
Smith, who collected 14 sacks last season, stayed in the game for one more play, but he was limping. Smith then waved on his replacement, Parys Haralson. Smith left the game and was not expected to return.
No word yet on how long Smith might be sidelined.
Update: Coach Jim Harbaugh, speaking to reporters after the game, suggested Smith was not injured seriously. "Preliminary, it looks like he'll be alright, dodged a bullet there," Harbaugh said.