Pettibone, 23, expressed a modicum of optimism Sunday. He said he hopes to return to full activity in "a few days." He is taking anti-inflammatory drugs.
"It's kind of the early stages of what happened last year," Pettibone said, "so it's good that we stopped it early."
Pettibone threw bullpens for two or three weeks in Florida before the soreness recurred. He figures to be the odd man out in the rotation picture, but a spot could be needed during the first few weeks of April while Hamels continues to build arm strength following a biceps tendinitis injury.
The Phillies do not possess extensive starting-pitching depth. Pettibone made 18 starts last season with a 4.04 ERA. Miguel Gonzalez or Ethan Martin could become the temporary fifth starter if the Phillies are without Hamels and Pettibone to start the season.
The talk of camp after the morning bullpen sessions was Kenny Giles, a 23-year-old righthanded reliever who throws 100 m.p.h. Amaro and other team executives focused on Giles while six other pitchers threw.
When Giles finished, Amaro asked catcher Cameron Rupp for an evaluation.
"He's got some hair on it," Rupp said. "He can put it where he wants it."
"Very impressive," he said.
Giles has never pitched above single A and was limited to 24 games because of two oblique injuries last season. His ERA there was 6.31, but he could quickly rise.
The Phillies designated Joe Savery for assignment to clear space for A.J. Burnett on the 40-man roster. Savery, the team's first-round pick (19th overall) in 2007, posted a 3.15 ERA in 20 innings last season.