Many factors contribute to the effectiveness any pass-rush effort. It's also not as easy as counting sacks, as Nick Saban is more than happy to point out.
Through three games, however, the effectiveness of Alabama to impact the opposing quarterbacks haven't been to the standard set in recent seasons. Sacks total five, good for 10th in the SEC. It also has five total quarterback hurries. A year ago, Alabama had nine sacks and nine hurries though three games.
The five injured linebackers and opposing offenses who threw quick passes contribute to the statistical differences. The return of Rashaan Evans in the middle and Anfernee Jennings on the outside should help since there hasn't been the same kind of push generated.