The Indianapolis Colts have the 2nd best best pass defense of the 2008 season through three weeks. This is most likely related to the fact the other teams run all over them and do not need to pass the ball. The same can be said about the Kansas City Chiefs and Houston Texans, too. With both teams, I wouldn't necessarily use their passing yards allowed (PYA) to determine whether I start WR Dwayne Bowe or whomever faces the Colts or Texans.
I am more inclined to pay attention to the rankings of the Baltimore Ravens, Tennessee Titans and Buffalo Bills. If I can afford to do so, WR Torry Holt is sitting this week against the Bills pass defense as is Bernard Berrian against the Titans. Harder will be the decision to sit Pittsburgh WRs Santonio Holmes and Hines Ward, but Baltimore has not allowed more than 100 yards passing in either of its first two games and the Steelers have a hurt QB and a sieve for an o-line.
More difficult is assessing the San Francisco 49ers rank. The team goes into New Orleans against a prolific passing attack. Given the Saints need to throw to move the ball, I can't see the 49ers preventing passing yardage on a scale anywhere close to what it has done in its frst three games (fewer than 200 yard in each). However, the Saints receiving corps is decimated by the losses of WR Marques Colston and TE Jeremy Shockey. Eventually, the receivers will stall the passing game. See Seattle Seahawks for proof.
Top 10 Pass Defenses: