Good question from Tre9er this week regarding the San Francisco 49ers' pass rush: "Is there info available breaking down how many sacks from Justin Smith and Ray McDonald have come from the base and nickel defenses?"

49ers Sacks by Personnel

Yes, there is. Nathan Jahnke of Pro Football Focus covered some of this ground Friday. I'll provide charts from ESPN Stats & Information showing the 49ers' sack numbers by defensive personnel and where they lined up on the field.

Justin Smith plays in all packages and produces from each as well. Rookie Aldon Smith, who has played mostly with the nickel defense, has collected all his sacks within sub packages (those featuring more than four defensive backs).

The 49ers have zero sacks from their defensive backs. That reflects the 49ers' ability to get sufficient pressure without blitzing. Opponents have attempted passes 19 times when San Francisco rushed a defensive back, the seventh-lowest figure in the NFL.

I'm most interested in seeing whether the Smiths, Justin and Aldon, can get pressure against the Cleveland Browns' Pro Bowl left tackle, Joe Thomas. The Browns will presumably try to run the ball, even if they do not gain many yards. That was their strategy against Seattle last week. But if the 49ers' offense scores enough points to force the Browns into more obvious passing situations, the Smiths could achieve more favorable matchups.

2011 Sacks: 49ers by Position on Field