SAN FRANCISCO -- For one backup quarterback, it was a first to remember. For the other, it was one to forget.
None of the Bears will want to dwell on this one, a 32-7 loss to the 49ers that dropped them to 7-3, while boosting the winners to 7-2-1.
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The Bears' Jason Campbell, subbing for concussed Jay Cutler, was making his first NFL start in 15 months and his first start for the Bears.
"Disaster" isn't a strong enough word to describe the outing -- the Bears' second straight loss.
By the time Niners backup Colin Kaepernick threw his second touchdown pass, just 3:55 into the third quarter, it already was 27-0, more points than the Bears had allowed in any game this season.
Clearly, the Bears' utter failure wasn't just Campbell's fault, although his 2 interceptions were costly. They couldn't run the ball either.
The offensive line didn't protect very well, allowing 7 sacks, although Campbell could have helped his own cause by getting rid of the ball sooner.
And the defense was missing in action for most of the night.
But the massacre brought back bad memories of the Caleb Hanie experience of a year ago, when the Bears went 0-4 behind their backup QB after Cutler fractured his thumb.
The veteran Campbell was brought in specifically to avert a similar nightmare, but the initial results were discouraging. The Bears had a total of 35 yards in the first half, including minus-1 yard passing. The offense failed to cross midfield before halftime.
The Bears started off trying unsuccessfully to establish the run, and Campbell completed just 1 of 3 passes and was sacked twice in the early going.
He was sacked three times in the first half, all by Aldon Smith, who came in with 9½, third in the NFL after 10 weeks. He had his way with left tackle J'Marcus Webb.
Smith finished with 5 sacks, choosing to abuse right tackle Gabe Carimi with a combination of bull rushes and inside moves in the second half.
Campbell's fourth pass was a weakly thrown sideline route to Devin Hester, whose sloppy pattern allowed Tarell Brown to jump inside him and pick off the pass.
That set up David Akers' 37-yard field goal that gave the 49ers a 20-0 lead with 6:32 left in the first half.
Later, Campbell badly overthrew Earl Bennett, which set up a 49ers field goal.
Kaepernick, the 49ers' 2010 second-round draft pick, was making his first NFL start in place of Alex Smith, who also was concussed a week earlier.
It was an impressive debut as he started off on fire, completing 9 of his first 11 passes for 170 yards and a touchdown, staking the home team to a 17-0 lead early in the second quarter.
It wasn't just the novice quarterback the much-publicized Bears defense couldn't control. Frank Gore and Kendall Hunter took turns gashing the visitors for big chunks of real estate. Gore had 3 runs for 33 yards to set up Hunter's 14-yard TD run.
Kaepernick showed off his arm strength early on a perfectly thrown deep ball for 57 yards to Kyle Williams, down to the Bears' 3-yard line. Bears nickel back Kelvin Hayden, who recently has been promoted ahead of D.J. Moore, was badly beaten on the play.
The 6-foot-4, 230-pounder demonstrated his touch on the next play, dropping a soft toss to tight end Vernon Davis for the score and a 10-0 lead with 6:14 left in the first quarter.
The 49ers drew first blood on Akers' 32-yard field goal with 4:28 elapsed. Kaepernick completed his first 4 passes for 45 yards, and the Niners were helped by a 15-yard personal foul on Bears safety Chris Conte.
The ensuing Bears possession ended when a tentative Campbell held the ball too long and was sacked for a 10-yard loss by Smith.
They didn't cross midfield until midway through the third quarter, when Campbell got the Bears on the board with a 13-yard scoring strike to Brandon Marshall.
Even after that score, the Bears still had been outgained 320-105 at that point.