When it rains, it pours. Right about the time that the Chicago Bears started their comeback and right about the time the San Francisco 49ers needed a strong drive from its offensive line, it started its decline. The 49ers didn't allow a sack in the first half, but allowed four in the second, including two on the potential game-winning drive.
The run blocking wasn't particularly strong for much of the game, but I thought the pass blocking was decent throughout the first half. Quarterback Colin Kaepernick had a bad game overall, and showed a troubling tendency to get himself out of the pocket before his protection actually broke down. Then in the second half, that protection ... broke down.
As usual, I'm here to break down every sack. One of them was "eh" and not really a sack per se, but it's officially credited as one so I'm going to show it.
First Sack: 10:26, 3rd Quarter: 1st and 10 at CHI 30: Kaepernick sacked for 0 yards (Stephen Paea)
Like I said, this one is a little ticky tacky. As far as who is to blame, I think there's plenty to go around. Left guard Mike Iupati never quite gets containment on his guy, and that forces Kaepernick to move first. Joe Staley has his man initially but at some point the whole thing breaks down. At some point, the entire line is just broken up and moved around -- which is how the play was designed, of course. I feel like Jonathan Martin did the best against his man on that play.
This is kind of one of those "pick your poison" plays when discerning who is at fault.
Second Sack: 11:01, 4th Quarter: 1st and 10 at SF 37: Kaepernick sacked for -5 yards (Shea McClellin)
This one isn't too hard to figure out. The right side of the line breaks down late, with Jonathan Martin's guy getting pressure on Kaepernick, as well as the guy Frank Gore ran into after the fake. But it's Staley and Iupati who eventually lose their guys to the outside, and both cut inside to level Kaepernick big time. Of course, I think Kaepernick held onto the football far too long on this play. He had some guys open and didn't take the shot.
Third Sack: 6:55, 4th Quarter: 1st and 10 at SF 20: Kaepernick sacked for -6 yards (Willie Young)
This was one of the most important drives of the game and Martin was solely responsible for the sack on this play. Young just beats him without too much issue. Martin backs up too far and gives up the inside line to Kaepernick, who was just about to fire off a pass to his left side. Not a good look, here.
Fourth Sack: 3:27, 4th Quarter: 2nd and 8 at CHI 43: Kaepernick sacked for -5 yards (Willie Young)
I guess you could argue that Alex Boone could have hustled back or something like that, but really, it's all on Martin here. Young beats him again, and handily at that. This was yet another huge play on a huge drive and it's not surprising that Kaepernick struggled in the second half given that he was almost constantly under assault. The offensive line broke down at the worst time, in other words.