SANTA CLARA, Calif. (AP) — AJ McCarron received high-fives from Andy Dalton's good hand, the one without the bulky cast protecting his broken right thumb.
And plenty of good jokes between possessions, too.
"When I came over, he told me what he saw and we kind of confirmed with each other," McCarron said. "Other than that, he was cracking some jokes and messing with me to keep me loose. That's just the way we are, that's our relationship. He was trying to be funny most of the time."
What mattered most to McCarron was staying steady and taking care of the ball.
His defense could take all the chances, and it did — forcing four turnovers.
Jeremy Hill ran for a pair of 1-yard touchdowns to back McCarron's first career start, with Dalton watching from the sideline. McCarron threw a 20-yard touchdown pass to Tyler Kroft just before halftime as the Bengals (11-3) took command against San Francisco (4-10).
The Bengals' lone previous victory on San Francisco's field was a 21-3 win at Candlestick Park in the teams' first matchup in 1974.
"I was happy for him," Dalton said. "It's never easy to win on the road."
Here are some things to take from this game:
DUNLAP'S DAY: Cincinnati's Carlos Dunlap forced a fumble against Anquan Boldin, recovered it and ran 21 yards in the second quarter to set up the Bengals' second touchdown as they scored three times in a span of 4:23.
He also blocked Phil Dawson's field goal in the fourth for his second such play this season. Dunlop has 10.5 sacks and Geno Atkins added two more to give him 10.
"Any time we can take points off the board, that's huge for our defense," Dunlap said. "We pride ourselves in that, not letting them score."
RUSHING STRUGGLES AGAIN: Hill and the running game struggled again after a poor showing against the Steelers.
A week after the Bengals managed only 64 yards rushing against the Steelers, they had just 68 against a San Francisco team that gave up 230 yards on the ground at Cleveland the week before.
"We were stagnant to start the game. There was a lot of stuff we wish we could have done better, especially in the run game," Hill said. "When you got some guys down, you're missing Tyler Eifert, and playing with a backup quarterback you've got to get the run game going."
Hill managed only 16 yards on seven carries against Pittsburgh — 12 of them on one play — and 31 yards on 19 carries Sunday.
OPPORTUNISTIC BENGALS: Three interceptions and a fumble.
The Bengals, who last month lost their only back-to-back games of the season, patiently waited for the mistakes to come then pounced.
Early in the second quarter, Adam Jones — back after a foot injury kept him out last week — intercepted a pass by Blaine Gabbert that bounced off McDonald's hands on a perfect pass and would-be first down. But the Bengals failed to make anything of that before capitalizing on the next Niners' miscue.
On third-and-10 from the 20, Carlos Dunlap stripped the ball loose from Boldin and returned it 21 yards to put the Bengals on the San Francisco 11. Hill scored his first TD on Cincinnati's ensuing possession, a play that was initially called no gain but overturned to a touchdown on review.
Shawn Williams made a pick on the goal line with 1:50 left.
"The turnovers were big defensively to jump start us a little bit," coach Marvin Lewis said.
ANOTHER FLOP AT HOME: The 49ers ran to their locker room down 21-0 at halftime to loud boos.
"I don't blame them. We're not playing good," wideout Torrey Smith said. "We're not fun to watch right now. Who wants to sit there and watch that?"
Levi's Stadium appeared about half-full at the start of the game but was far closer to empty by the fourth quarter.
San Francisco went 2 for 14 on third down and secured last place in the NFC West for the first time since 2005. The Niners also had 11 penalties for 98 yards.