SEATTLE (pick) 23 Jacksonville 21
Jacksonville is proving to be a pretty good team, as their offense has been 0.6 yards pe rplay better than average so far this season (5.9 yppl against teams that would allow 5.3 yppl to an average attack), while the Jags' defense is only 0.2 yppl worse than average despite allowing 6.1 yppl (to teams that would combine to average 5.9 ypppl against an average team).
The Seahawks are having all sorts of injury issues to all parts of their team (All-Pro OT Jones, QB Hasselbeck, DE Kearney, etc, etc) and that has affected their level of play. Seattle has been out-gained averaged just 4.9 yppl (against teams that would allow 5.0 yppl to an average team and there really isn't much difference between backup Seneca Wallace and starting quarterback Hasselbeck (at least their wasn't last season).
The Seahawks' defense has allowed 5.9 yppl to teams that would average 5.3 yppl against an average team, but their run defense is much better than the 5.2 ypr that they've allowed on the season, as 159 yards came on just 2 plays by San Francisco's Frank Gore.
Seattle has allowed an average of just 81 rushing yards at 3.7 ypr in their other 3 games (against teams that would average 4.2 ypr), which I believe is more indicative of their true run defense. The defense is still a bit worse than average with the injuries to Kearny and CB Josh Wilson and Seattle is certainly at a disadvantage from the line of scrimmage in this game.
My math model actually favors Jacksonville by 4 points but Seattle applies to a very strong 63-19-6 ATS bounce-back situation while the Jaguars apply to a negative 29-74-1 ATS situation. I'll go with Seattle to squeak out a victory based on the strong situation. I'll consider Seattle a Strong Opinion at +3 regardless of whether Hasselbeck returns at quarterback.