Where are you guys getting the 4 sacks allowed figure?
According to profootbalfocus.com, he has allowed 2 sacks, 1 QB hit, and 3 pressures.
PFF - Tackles stats and ratings
By contrast, our left tackle (the one who has started the majority of games), has 5 sacks, 5 QB hits, and 17 pressures.
For comparison purposes, Joe Thomas has 2 sacks, 3 QB hits, and 4 pressures. Jake Long has 3 sacks, 2 QB hits, and 4 pressures.
You can go to the linked site to get the stats for all of the tackles.