The problem with losing a pass rusher

Did anyone notice last year that the pass rush looked really bad? In my memory, the low point was actually a game the team won. In week 12 against the Cardinals, Kurt Warner, playing in a wheel chair, threw for almost 500 yards. Take a look at the game clips - Warner drops back, sees his number one option is covered, remembers he forgot to send his pastor a thanksgiving card, takes a shower, shaves, sees his number 1 option is still covered, re-grows a beard a la Charlie from P.O.5, and throws a 50-yard touchdown.

As any casual observer of the füsball knows, teams can't win without pressuring the quarterback. Teams that get sacks win, while teams that don't get sacks lose. There's evidence suggesting that losing even one pass rusher from your roster is enough to send a defense from better-than-average to worse-than-average. And here's the kicker - when teams that lose a pass rusher try to replace that pass rusher via free agency or a trade, they still decline. Schatzy from Football Outsiders makes the case:

Does adding a top pass-rusher help as much as losing a top pass-rusher hurts? No, not even close. In fact, top pass-rushers switching teams have an effect roughly opposite that of top offensive linemen switching teams: Offensive linemen tend to have a bigger impact on their new teams, while top pass-rushers tend to have a bigger impact on the teams that lose them.

I mention all this just to show that a team needs a pass rush to be successful in the NFL.

As I stated in the opening, it seemed to me like the 2007 49ers couldn't sack groceries. Unfortunately, it appears I was right. According to Football Outsiders, the 49ers D-Line ranked 25th in adjusted sacks (sacks per pass attempt adjusted for opponent, down, and distance). The defense overall ranked 29th in DVOA against the pass. What did they do this offseason to improve their pass rush? Watched their leading pass rusher retire and replaced him with a guy who piled up all of two sacks last year (and who bears a remarkable resemblance to this guy). This doesn't inspire much optimism.