...IF...the Red Sox are serious about getting him three minor league starts.
The plan appears to be for Buchholz to begin on Sunday. That would mean (given a five-man rotation, four-days between starts) his next starts would be August 30th and September 4th. However, most minor leagues end regular season play two days earlier on September 2nd.
That sets up the minor league post-season start scenario with AAA Pawtucket and High-A Salem both seemingly likely play-off teams in their respective leagues.
There would be a third option, but maybe a less attractive one from a competition standpoint. Short-season Class-A Lowell has a game schedule for the 4th at Aberdeen, but teams in the NY-P League are generally stocked with players new to professional baseball, not likely what the Red Sox would envision for Buchholz' final tune-up.