Commenter Hoo (this really sounds like the beginning of a bad comedy bit doesn't it?) asked a good question. Why the hell have his surgery now? Why not have it in November or December? A 3 months recovery time then would have been perfect.
According to the Post - the hip has been an issue for a year or so. That makes it seem like they could have gone ahead and done it at the end of last season. According to Zuckerman and other sources, though - the injury didn't happen until last month. It sounds conflicting but it probably isn't. Most likely Detwiler hurt his hip last year and pitched through it. When the season ended he hoped with an extended rest he'd be ok. Unfortunately once he started up again, getting ready for this year - it got aggravated again or was made worse.
Of course that's all well and good if it was just a case of Detwiler being like every other minor leaguer (and like most normal people everyday in fact), working through pain and hoping whatever is wrong will just go away. HOWEVER, if the Nats knew that Detwiler was having issues, they really should have taken a look at it at the end of last season. I don't know what they knew, but I know what I know, which is I don't see any reason to give this team's management any benefit of the doubt. Maybe I should though, because they've always been on top of injuries.