"Phillies right-hander Roy Oswalt, who hasn't pitched in more than a month because of bulging discs in his back, is set to make his first minor-league rehab stint on Wednesday, Phillies Assistant General Manager Scott Proefrock said Sunday, before the Phillies-Padres game at Citizens Bank Park.

Oswalt hasn't pitched since complaining of back discomfort after a two-inning, four-run stint against the Cards in St. Louis on June 23. He was placed on the 15-day disabled list the next day.

Proefrock said Oswalt will pitch Wednesday for the Lehigh Valley Iron Pigs, who are scheduled to face the Pawtucket Red Sox at 7 p.m. Wednesday at Coca-Cola Park in Allentown, Pa.

Oswalt, who turns 34 next month, was 4-6 with a 3.79 ERA in 13 starts before going on the disabled list. After opening the season with a 2.70 ERA in his first nine starts, he allowed 17 earned runs and 32 hits in 26 1/3 innings in his last four starts -- a 5.81 ERA and 1-4 record during that span.

During his stay on the DL, Oswalt has undergone treatment with both anti-inflammatory injections and strengthening exercises.

Oswalt was 7-1 with a 1.74 in 12 starts after the Phillies acquired him from the Astros a year ago.

In Oswalt's absence, 23-year-old rookie righty Vance Worley has emerged as an effective big-league starter, going 6-1 with a 2.02 ERA in 10 starts. Since Oswalt last pitched, Worley is 4-0 and has allowed only three earned runs and 16 hits in five starts in 33 1/3 innings for 0.81 ERA.

Proefrock wouldn't speculate on how many rehab outings Oswalt might need before being activated but he said it would be far fewer than Brad Lidge's eight, who missed the entire preseason. Most likely, if all goes well, the Phillies would activate Oswalt in early August after three or four rehab stints."