The Jags play the Colts tough, the last 5 years of Colts-Jags matchups the margin of victory has been, 2, 4, 7, 2, 22, 3, 7, 27, 7 and 8. 8 of the last 10 matchups have been within a single score margin, with one blowout for each side. Despite this history, it's hard to look at how this Jags team has fared against the pass and not be excited.
Through 3 games the Jags opponents have passed to the tune of 60 for 93 (64.5% comp), 867 yards (9.9 per attempt, 14.5 per completion), 7 TDs with 3 picks and 7 sacks. This all totals to a passer rating against of 108.7, 8.1 ANY/A and a pass defense VOA of 47.8% (4th worst in the league).
3 games isn't a big sample and very subject to strength of schedule. Philly (14th), San Diego (8th) and Denver (4th) are all above average passing offenses by VOA, but with no opponent adjustments, and their game against the Jags factoring into their rating significantly it's still a bit of chicken and egg.
Denver, the Jags week 1 opponent, had it's least productive game by YAR against Jacksonville but was more efficient against Jacksonville than Indy (125 on 36 dropbacks vs 147 on 57 dropbacks) with Denver's best game coming against the Seahawks week 2. Denver's #4 ranking doesn't seem to be wholly result of beating up on the Jags.
On the other hand, week 2 against the Jags was by far the Chargers best passing game to date, with a 30 dropback for 143 DYAR day standing in deep contrast to 57 for 127 and 40 for 56 outings. Likewise for the Eagles, their matchup with Jacksonville was their best day through the air, but Michael Vick settling into his starter role is also a plausible explanation.
So the Jags past schedule of pass Os may very well have been tougher than most, it's impossible to attribute the entirety, or even the majority of the Jags struggles against the pass to their strength of schedule.
The Jags D appears to be pretty bad, but where is it bad? The Jags 7 sacks so far on the season are already half their embarrassing 2009 total of 14. While a pass rush was glaringly absent from the Jags 2009 pass D, it actually seems like the strong point of the 2010 edition. The Jags real issue appears to be in the secondary. The Jags rank dead last in VOA vs #1 WRs and are allowing over 100 yards per game to them. This is especially glaring since you'd be hard pressed to find a "#1 WR" in Seattle, (a sans-Vincent Jackson) SD, and Denver. Against #2 WRs they rank 30th by VOA, with more middling rankings against "Other WRs" (18th), TEs (18th) and RBs (16th).
The Jags struggle against receivers out wide, and the problem seems to be allowing them to get deep as the Jags D has allowed more passes over 20 yards (16), more passes over 40 yards (6) and a higher % of passes going for 1st downs (44.1%) than any other team in the league.
It seems like a very good week for Garçon to show up healthy with his good hands on. There are a number of deep sideline routes with his name on them.