PHOENIX — Roy Halladay will undergo arthroscopic shoulder surgery Wednesday in Los Angeles, the Phillies announced Thursday. Neal ElAttrache, the renowned orthopedist who diagnosed Halladay's injury, will perform the procedure.

An initial diagnosis based on an arthrogram revealed a partial tear to Halladay's rotator cuff and fraying of his labrum, both of which were caused by a bone spur in his shoulder.

The Phillies do not have a timetable for Halladay's return because the true extent of damage to Halladay's shoulder will not be known until ElAttrache operates.

Halladay said he received no indications from the doctor that there could be more problems than originally believed.

"The timetable is going to come once they go in and confirm that, 'Hey, what we saw in the x-rays is exactly what we saw when we went in there,'" Halladay said. "And then I think that will give us a better idea of the timetable. But they were definitely optimistic that I would be back this year."

Have a question? Send it to Matt Gelb's Mailbag.