Green Bay grabbed a quick 7-0 lead on Shields pick-six with 12:48 still left in the first quarter.
On second-and-6, Kaepernick initially looked toward the right sideline, but when Crabtree slipped and fell, he scrambled to his left. Under pressure, Kaepernick threw off his back foot, trying to hit Davis, but Shields knifed in front for the interception then headed down the sideline.
After Kaepernick dove and missed at the 20, Shields cruised into the end zone.
The 49ers answered on their next drive, marching 80 yards in seven plays for a touchdown, Kaepernick scoring on a 20-yard scramble. Kaepernick made a huge play earlier in the drive, facing third-and-10 from the 49ers 33. He scrambled left then lofted a short pass over Woodson to Gore, who ran all the way to Green Bay 22 for a 45-yard gain.
Packers linebacker Clay Matthews sacked Kaepernick for a 7-yard loss on first down, but Gore gained 9 yards on a second-down draw. On third-and 8 from the 20, Kaepernick dropped back to pass but saw a huge alley open up off the left edge and took off running. He didn't stop until he was in the end zone, tying the game 7-7 with 9:01 left in the first quarter.
"When you see a quarterback run the way he runs, that's unbelievable," 49ers linebacker Patrick Willis said. "It amazes me. It wows me. It's like, 'Wow! Did he just do that?'"
The Packers moved back ahead 14-7 with 29 seconds left in the first quarter on Harris' 18-yard burst up the middle for a touchdown. One play earlier, Rodgers hit Jones on a 44-yard strike down the right sideline. Jones got behind 49ers nickel cornerback Chris Culliver and made a leaping catch before safety Dashon Goldson arrived.
The 49ers capitalized on a Packers turnover to pull even. Green Bay's Jeremy Ross muffed an Andy Lee punt, and 49ers cornerback C.J. Spillman recovered at the 9.
"There's no excuses for it," McCarthy said of Ross' turnover. "It was not a difficult punt. I tuned into seven points for the 49ers."
On third-and-goal from the 12, Crabtree ran a crossing route over the middle, and no Packer covered him. Kaepernick hit Crabtree in stride, and he scored with 10:59 left in the half, making it 14-14.
The 49ers quickly got the ball back as cornerback Tarrell Brown intercepted a Rodgers pass and returned it 39 yards to the Packers' 48. Eight plays later, Kaepernick threw a 20-yard laser for a touchdown to Crabtree, who beat Shields on a post pattern. Crabtree's TD put the 49ers ahead 21-14 with 3:53 left in the half.
"It was a shootout," Crabtree said. "We knew those guys could put up points."
Rodgers fired a 20-yard touchdown strike over the middle to Jones with 2:33 left in the half, tying the score again. Kicker David Akers made a 36-yard field goal on the final play of the half, putting San Francisco ahead 24-21.
NOTES: Packers wide receiver Donald Driver, in his 14th NFL season out of Alcorn State, was active for Saturday's game. He was inactive for the regular-season finale and for last week's playoff victory over Minnesota. ... Niners kicker Billy Cundiff was inactive, leaving all of the kicking duties to the struggling Akers. San Francisco signed Cundiff on Tuesday as a free agent to compete with Akers. ... The 49ers had 579 total yard of offense to 352 for Green Bay. They controlled the ball for 38:01 to 21:59 for the Packers.