The 47-year-old left-hander was hurt Tuesday and general manager Ruben Amaro Jr. said he had a sprained ulnar collateral ligament and a strain of the flexor pronator tendon. Amaro said that Moyer would be out indefinitely, but the team hadn't determined Thursday whether he'd require reconstructive surgery.
Among the tests Moyer had yet to undergo was an ultrasound, Amaro said. Moyer returned to Philadelphia earlier in the week.
"He's going to be out quite some time," Amaro said. "He had some discomfort in the elbow earlier and I think it just got to the point where it became a real issue."
Kyle Kendrick, optioned to Triple-A Lehigh Valley after surrendering three homers in one inning in his last start, will be recalled and pitch in his regular spot on Saturday.
The Phillies plan on recalling left-hander J.A. Happ to replace Moyer on Sunday.
Earlier in the week, Amaro had sounded optimistic the team would acquire a pitcher. He declined to say Thursday whether pitching was still a priority at the trade deadline or whether the Phillies had deals in the works.
"I'm not going to get into that," Amaro said.
Pitching coach Rich Dubee expected Kendrick to bounce back from the mental blow he absorbed earlier in the week.
"You'd better be flexible in this game, that's for sure," Dubee said. "It's another opportunity."
Moyer is 9-9 with a 4.84 ERA and left-hander Cole Hamels said he's been a mentor to the rest of the staff.
"No disrespect to Jamie, but he's been a pleasant surprise after not being in the rotation last year at the end of the year and coming off two surgeries," Amaro said. "He's been in a lot of ways a godsend, he's pitched quite well under the circumstances."
Happ won 12 games as a rookie last year but has been hampered by a left forearm strain since April and was sent to the minors earlier this month after making six rehab starts.