The 49ers capitalized on a Lacy fumble -- forced by outside linebacker Aldon Smith and recovered by cornerback Tarrell Brown at the Green Bay 14 -- to regain the lead.
Kaepernick connected to Boldin for a 10-yard touchdown with 8:57 remaining in the first half, putting the 49ers up 14-7. Lined up left, Boldin ran a quick slant, grabbed Kaepernick's pass, slipped a tackle and bolted into the end zone.
Facing third-and-6 from the Packers' 10 earlier in the drive, Kaepernick scrambled to his left and out of bounds for four yards, but Green Bay linebacker Clay Matthews delivered a late hit -- a forearm across the throat -- drawing a flag. Niners offensive tackle Joe Staley quickly confronted Matthews, drawing a flag for unsportsmanlike conduct as the two teams pushed, shoved and yelled along the sidelines.
"First off, it wasn't a very smart play," Matthews said. "I had already committed to hitting the quarterback. I guess I should have figured he was going to step out of bounds, but it was nothing personal. I went up to him later and was joking around with him."
The offsetting penalties occurred after the play, but the officials still had the Packers and 49ers replay third down. Referee Bill Leavy admitted after the game that the officials erred in administering the offsetting dead-ball penalties and that it should have resulted in a fourth down for the 49ers.
Kaepernick hit Boldin for a touchdown when they replayed the down.
In a post-game statement, Leavy said: "On the play where the quarterback (Kaepernick) went out of bounds and was hit late out of bounds. And then there was a subsequent hit by a San Francisco player. The down should have counted. The penalties were both dead ball, and they should have offset at the spot where the runner went out of bounds. And it would have been fourth down."
Green Bay pulled even again with 16 seconds left in the half on Rodgers' 12-yard touchdown pass to tight end Jermichael Finley. Rodgers hit Finley with a quick pass along the right sideline. He broke cornerback Perrish Cox's tackle and powered into the end zone. Earlier in the drive, Rodgers hit Nelson for 15 yards on third-and-15 from the 49ers' 39, many of those yards coming after Asomugha whiffed on a one-on-one attempt to tackle the wide out.
NOTES: Jerron McMillian started at free safety for Green Bay in place of the injured Morgan Burnett (hamstring). ... Rookie FS Eric Reid, a first-round pick out of LSU, started for the 49ers in his NFL debut and had his first career interception.