"You can call it a setback now. And it might be severe enough to keep Johan Santana from pitching in the majors this season.

Santana feels "lingering discomfort" in his surgically repaired left shoulder and instead of making another rehab start later this week he will fly to New York and see Met doctors Thursday, Mets GM Sandy Alderson said Tuesday.

"We want to make sure that's checked out before we go any further with the rehab," Alderson said. "I can't comment on the severity of this discomfort - that's one of the reasons we want him seen by a doctor. But there is some there. More than anything else, Johan would like to have it checked out before he proceeds."

When Alderson announced Monday that Santana's rehab schedule would be pushed back a day, he said he didn't view it as a setback, more like a schedule tweak. But the GM acknowledged Tuesday it's something more.

All along, Santana himself has preached caution about his recovery, even though he reached 90 mph on the radar gun in his first rehab start last Thursday for Single-A St. Lucie. He threw three scoreless innings that night and while he said he'd like to pitch for the Mets this season, he seemed to realize his recovery could be unpredictable.

The day after his start, he played catch, including a significant session of long-toss, at the Mets' minor-league complex in Port St. Lucie and said he was surprised by how good he felt. Something clearly has changed since then - he skipped the bullpen session that was supposed to follow the next day - and it could affect whether Santana pitches at all this season.

"It was a day-by-day proposition to see how he came back after his original three innings," Alderson said. "He has less confidence than he might have had, so I think it's prudent to have it checked out and it'll either be reassuring or, you know, we'll step back and see where we are."

Asked if he was tempted to simply eliminate the idea that Santana could pitch for the Mets this season, Alderson said, "No, because I don't really believe this is about this year."