Perhaps some overanalysis is being conducted here, but I'll jump in. Particularly since it was Beckett's RIGHT oblique, to the extent he was hampered by the strain, I think you could make a case that the result on his mechanics would be that he would tend to stay relatively closed throughout the deliver as opposed to opening up. There'd be a loss of rotational torque towards the release and follow through of his delivery...resulting in less movement, not more. At leats that's my thoughts, I suppose ya never know if perhaps it is bothering him to some extent.
At any rate, I think his struggles might tell us, or hinge upon, two things and this builds on a couple of the views expressed here today:
(1) The layoff left him rusty
(2) 2008 Beckett
Knowing Sox management, I imagine the FO is watching VERY closely to see how Beckett, assuming he has additional starts this post-season, performs as he enters his last year before the team option. Hate to say it, but despite his importance in the Sox capturing the 2007 WS title, with this FO, Beckett still needs to "prove himself" if he's to get extended beyond 2010 either during this offseason or any time prior to the close of the 2009 season.
If the Sox advance, but Beckett throws like crap a couple more times, especially if there is no oblique strain to blame it on, the FO will start to question his ability, and an offseason extension will be unlikely. And if he's less than stellar early in 2009, I'm afraid things could get ugly.