Two tweets from Phillies beat writer Matt Gelb:
A Phillies official says Roy Oswalt has left the team for personal reasons. No expected return date.
Oswalt was not removed from the game for those personal reasons. He was taken out by Manuel because of his ineffectiveness.
Speculation at this point about "personal reasons" is obviously pointless.
If Oswalt isn't available for some time, the obvious candidate to replace him is Kyle Kendrick, who started 31 games for the Phillies last year. But Kendrick, in the bullpen this season, hasn't thrown more than 42 pitches in a game and probably couldn't be counted on for more than four or five innings in a spot start.
If the Phillies dip into their system, the best candidates at Triple-A are probably Eddie Bonine, who's got some experience in the majors and has pitched well this season, and 23-year-old Vance Worley, who's pitched exceptionally well this month and was ranked this winter by Baseball America as the Phillies' 11th-best prospect.