I've long thought that the Cover 2, and the Tampa 2 in particular, was designed to counter the Walsh style offense. The Tampa 2's emphasis on quick defensive linemen who disrupt the quarterback's timing, the use of short zones to allow completions but limit yards after catch while potentially being able to jump the route, and a simplified coverage system that is less likely to cheat linebackers to the left or right therefore opening up cutback lanes in the rushing attack, is ideally suited to disrupting the Walsh offense.

So I decided to see how Seattle has faired against Cover 2 defenses the past three years. Each perfomance is measured with DVOA, so that the quality of the defense doesn't skew the numbers.

2004
@TB -40.5%
STL 13.2%
@STL -10.9%
@NYJ 4.1%
STL 11.1%

Average offensive DVOA versus Cover 2: -22.42
Overall offensive DVOA: 4.0%

That last one is the infamous "We want the ball and we're gonna score" game. Lovie Smith was Saint Louis's defensive coordinator until 2003 and Larry Marmie, his replacement, used a variation of the Cover 2. That total is pretty heavily influenced by week two's matchup against the Bucs, where the Hawks were absolutely stifled, gaining a mere 182 yards.

2005
@STL 33.0
STL 12.0
IND 62.1

Average offensive DVOA versus Cover 2: 35.7
Overall offensive DVOA: 23.4

I might just drop that game in Indianapolis as the Colts were 13-1, gave Peyton Manning most the night off and, most importantly, played without Bob Sanders, Cato June or Dwight Freeney. The tricky part is extracting that game from the Hawk's overall offensive DVOA.

Let's try these numbers instead.

Average offensive DVOA versus Cover 2: 22.5
Overall offensive DVOA: 19.52

The overall is a little crude because I ended up just taking the Hawks' Offensive DVOA for the Colts game, dividing it by 16 and then subtracting that from their cumalative Offensive DVOA. That fails to account for the different number of offensive plays between games, but while rough, I think it's better than leaving in a game where Indy was clearly not sending out their best unit.

2006
@DET -26.7
@CHI -30.7
MIN -45.2
KC -21.0
@TB 15.5
@CHI 16.9

Average offensive DVOA versus Cover 2: -15.2
Overall Offensive DVOA: -11.7%

Average offensive DVOA versus Cover 2 2004-2006: -4.94
Average offensive DVOA 2004-2006: 11.82

This is about what I expected. Seattle performs significantly worse against teams that employ a Cover-2/Tampa-2 scheme. While I think Seattle is clearly the better team, this might be a closer than expected contest thanks to Monte Kiffen's brainchild.