After learning that Chien-Ming Wang suffered a setback in his rehab while playing catch yesterday, manager Joe Girardi sounded a bit worried.

"We did express some concerns about the depth of our starting rotation right now,'' Girardi said of a recent discussion he had with managing general partner Hal Steinbrenner about the current state of the team.

Wang, who was placed on the disabled list July 5 with a right shoulder strain, was sore after his throwing session. He originally was scheduled to throw again Tuesdaybut will not resume activity until Friday.

"The pain I felt today was normal," Wang said. "It might go away. It's not too bad."

"So-so'' was how Girardi characterized Wang's session yesterday. "He's not going to throw for another four days. He had some tenderness in his biceps. It's all interrelated, so we're going to give him a few more days and some more strengthening before he goes back out.''

With this most recent snag in Wang's recovery, Girardi is less optimistic about his return.

"It's not what you want to hear,'' Girardi said. "We were hoping that two weeks' rest would be enough to get him on a throwing program. Does it mean that he won't be pitching again this year? No, I'm not saying that, but it's not going to be assumed as we thought because we're going to be taking a couple more days off.''

When asked about seeking outside help to bolster the rotation, Girardi deflected questions to general manager Brian Cashman, but the Yankees don't have a plethora of options internally.

"That was one of the things I have concerns about,'' Girardi said. "That if we have another injury, where do we go?''

Current starters Joba Chamberlain and Andy Pettitte already have provided enough anxiety about the depth of the starting rotation, and with the emergence of Phil Hughes and Alfredo Aceves as successful relievers, the Yankees are somewhat hamstrung.

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Girardi said Hughes, who struck out eight in three innings against the Tigers over the weekend, has become too valuable as the eighth-inning guy to put back in the starting rotation. He also said the time it would take to stretch him out and build him back up to a higher pitch count is prohibitive.

The more likely reliever to be converted back into a starter is Aceves, Girardi said. But after he gave Aceves a spot start against the Twins, Girardi noted the negative effect it had on the bullpen during the subsequent Angels series.

In Wang's absence, the Yankees have been forced to call upon minor-leaguer Sergio Mitre to assume the role of No. 5 starter. After Mitre - who will make his first major-league start of the season tonight - the Yankees' internal options are very limited. Given that Kei Igawa is the next in line, Mitre is realistically their last stop, barring a trade.

But acquiring Toronto's Roy Halladay remains unlikely, and beyond Halladay, there is a dearth of candidates who pique the Yankees' interest.