Backe out with elbow tightness. Arias will start in his spot. LINK
Why not move Wolf up to today to start on normal rest? Was (at least) a day and a half's notice not enough for Wolf to get ready?
Moving Wolf up from Tuesday to Monday would also mean Wolf would get an extra start on the season's final day. However, I'm sure Wolf and others sans Oswalt appreciate getting an extra day's rest this time of year.
I don't think this came into play at all, but the big elephant in the room is that Wolf has 500,000 reasons to get a chance at 200IP. Wolf needs to average 8.25 IP per start to get there on 4 starts and 6.6 IP per start to get there on 5 starts.