ST. LOUIS A 49ers defense missing its spiritual leader and its top pass rusher seemed susceptible to slipping Thursday in St. Louis.
Instead it had its most dominant effort of the season, forcing 11 Rams punts, two Rams turnovers and holding them to a paltry 18 rushing yards.
"If a link gets taken out of the chain, somebody needs to step up," said linebacker NaVorro Bowman, who led San Francisco's defensive effort with two sacks and three tackles behind the line of scrimmage.
Inside linebacker Patrick Willis sat out the game with a groin injury.
Aldon Smith, meanwhile, is seeking treatment after crashing his truck and being arrested for DUI last week.
Despite not playing, Smith increased his sack total when the NFL ruled that he, not Justin Smith, took down Colts quarterback Andrew Luck on Sunday.
Aldon Smith now has 41/2 sacks to lead the 49ers.
Dan Skuta replaced him in the starting lineup and rookie Corey Lemonier entered in obvious passing situations. The 49ers sacked St. Louis' Sam Bradford five times and hit him an additional eights times. Ahmad Brooks had 11/2 sacks.
Safety Donte Whitner grabbed his first interception of the season after he gathered in an end-zone pass from Bradford that had been tipped by Tramaine Brock, who was filling in for injured Nnamdi Asomugha.
It could have been even more one-sided. Whitner dropped an easy interception the deflection was caught by the Rams while Bowman let what would have been an interception and touchdown return slip through his hands.
Michael Wilhoite made his first-ever start in place of Willis and had five tackles.
Wide-receiver shuffle Hoping to spark a slumbering offense, the 49ers gave rookie Quinton Patton, not Kyle Williams, the nod as the No. 2 wide receiver against St. Louis. Patton, however, suffered a foot injury after just one catch for zero yards and did not return. Williams resumed his role and finished without any catches.
Meanwhile, Jon Baldwin made a solid debut as a 49er, catching a 14-yard pass on third-down in the third quarter. The 49ers swapped A.J. Jenkins for Baldwin, a former first-round pick by Kansas City, last month. He had a second catch for four yards later in the game.
"I've got a good feeling about him," 49ers coach Jim Harbaugh said of Baldwin.
Just for kicks When the 49ers forced a Rams punt late in the first half, they opted for a seldom-seen play with four seconds remaining a free kick from their own 39-yard line.
The 49ers lined up as if they were kicking off but had Andy Lee hold the ball for kicker Phil Dawson. Had the 71-yard attempt been good, it would have been worth three points.
It wasn't. Dawson's attempt was short and too far to the left, and the Rams returned it out of the end zone for a short gain to end the half.
Dawson, who had made seven straight field goals from 50 yards and beyond, was wide right on a 53-yard try on the 49ers' opening drive.
Injuries Harbaugh said the 49ers "dodged a bullet" when starting left tackle Joe Staley went down with 1:50 remaining and had to be helped off the field. A few minutes later Staley emerged from the X-ray room on his own without a limp. "He's going to walk it off," Harbaugh said.
Both guard Mike Iupati and cornerback Tarell Brown also received X-rays. Neither injury is considered serious.
Read Matthew Barrows' blogs at www.sacbee.com/sf49ers and listen for his reports Tuesdays on ESPN Radio 1320.