Halladay was actually set to make a minor-league rehab start, but the club unexpectedly announced that he'll instead start for the Phillies against Arizona Sunday.
Halladay's been recovering from surgery to clean up bone spurs, a frayed labrum and a partially torn rotator cuff back in May.
With the Phillies not in playoff contention, they didn't have a great need for him to return, but Halladay himself has one. He's a free agent after the season, as he's not going to have enough innings pitched for his $20 million option for 2014 to vest.
Halladay, 36, is 2-4 with an 8.65 ERA, 1.46 WHIP and 35 strikeouts in 34 1/3 innings this season. He's an eight-time All-Star and two-time Cy Young winner. In two minor-league rehab starts, he allowed four earned runs on 13 hits in 12 innings pitched, good for a 3.00 ERA and 1.58 WHIP. He struck out eight and walked six.