A) Buehrle could probably go on 3 days rest multiple times and be fine. The guy is a horse and hasn't missed a start in like 6 seasons or something. But you don't risk anything when the season is shot.
If you need a call up for a 6th starter, is it better to do it on the double header day??
If they stuck with the current 5 only it would be back to Buerhle. The double header moved things up a day is the problem, so he would be going on 3 days rest.
Also, Brandon Morrow and Ricky Romero will pitch 3-4 games each in September and look OK, and thus will be counted on as starters for next year. Naturally, both will then go MIA as of mid April 2014 leaving the starting rotation in shambles yet again.