Frank Gore motored to his right before running into a road block.
He slammed on the brakes and took a detour to his left, leaving one Ravens defender in his dust before defensive end Cory Redding spun him down in the backfield for a one-yard loss.
That negative run was a microcosm of Thursday night for the San Francisco running back, his wheels spinning in place -- and the 49ers offense stuck in the mud -- in a Ravens' 16-6 win. Gore ran for 39 yards on 14 carries against a Baltimore defense playing without linebacker Ray Lewis (toe) for a second straight game. His backup, Dannell Ellerbe (thigh), was inactive, too.
Gore's backup, Kendall Hunter, had four carries for 14 yards as the 49ers, who entered Week 12 with the NFL's sixth-ranked running attack, finished with 74 rushing yards on 21 carries.
"I don't think you could have stopped the run any better," Ravens coach John Harbaugh said.
San Francisco's game plan was clear heading into the Harbaugh Bowl. The 49ers rolled into M&T Bank Stadium with a 9-1 record thanks in large part to the damage Gore has done running behind his beefy offensive line. With Gore averaging 4.6 yards per carry entering the game, the 49ers had hogged the ball this season, making things easier for quarterback Alex Smith and keeping the 49ers defense fresh.
But on Thursday, the Ravens got excellent penetration up front and stuffed Gore when he ran up the middle. When he bounced it outside, he didn't find much running room there, either.
With the threat of the run gone, the Ravens unloaded on Smith, sacking him nine times.
"We really wanted to make them one-dimensional," outside linebacker Terrell Suggs said.
Second-year linebacker Albert McClellan, who was a surprise selection for the team's 53-man roster at the end of training camp, got his first career start at inside linebacker alongside Jameel McClain.
"He did a hell of a job," said linebacker Brendon Ayanbadejo, who also got plenty of snaps. "We're playing linebacker by committee, especially with Ray Lewis down. It's all hands on deck right now."
McClain racked up eight tackles, tying him for the team lead with strong safety Bernard Pollard. McClellan, Ayanbadejo and outside linebacker Jarret Johnson each added four tackles.
Gore's longest run was nine yards and the 39 yards were his second-lowest rushing total of 2011.
Gore strung together five straight 100-yard rushing performances until his streak was snapped in the 49ers' Week 10 win over the New York Giants. In that game, he ran for zero yards on six carries before a knee injury knocked him out of the game. He bounced back last week with 88 yards against the Arizona Cardinals, but he was still limited in practice this week by the injury.
A bad wheel didn't appear to slow Gore down in this one, just a Ravens defense that wouldn't allow him to get out on the open highway.
"We played a gap-control, knock-em-back type of defense," Ayanbadejo said. "You're not going to be able to run sideways and cut back and do all of these things on us. If you're going to run on the Ravens, you're going to have to run downhill and break a tackle."