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3/23/2013 9:30 A.M. ET

Johan unsure when he'll return to the mound

Two-time Cy Young Award winner continues to be bothered by shoulder weakness

PORT ST. LUCIE, Fla. -- A downtrodden Johan Santana insisted Saturday that he is not worried about missing a significant chunk of the regular season, but he has no idea when he might be able to return to the mound.

"I'm making progress," Santana said. "It's just I don't know when I'm going to be pitching again."

The left-hander's comments came one day after Mets manager Terry Collins acknowledged that Santana will not break camp with the rest of the team. Neither Collins nor general manager Sandy Alderson has gone as far as to say that Santana will start the season on the disabled list, though his placement there appears to be a formality at this point.

Santana, who threw a full bullpen session and long-tossed at distances up to 180 feet earlier this spring, has not pitched off a mound for more than two weeks due to left shoulder weakness. He is currently playing catch at 90 feet in what he called "a slow process."

"It's not as strong," Santana said of his shoulder. "I'm just building up my strength. We've just got to wait until we start competing and see how it reacts."

Santana was a first-half sensation last season, going 3-2 with a 2.38 ERA from Opening Day through his June 1 no-hitter. But back, ankle and shoulder troubles began irking him around midsummer, resulting in a 3-7 record and 8.27 ERA from that point forward. He went 0-5 with a 15.63 ERA over his final five starts of the season, prompting the Mets to place him on the DL.

Over the ensuing offseason, his third since undergoing major left shoulder surgery in Sept. 2010, the left-hander did not throw at his homes in Venezuela and Florida. Instead, Santana chose to give his arm as much rest as possible.

The two-time Cy Young Award winner did not anticipate that decision resulting in shoulder weakness, which is now threatening a significant portion of his season. To the contrary, Santana threw two bullpen sessions in the early days of camp before the Mets noticed a lack of velocity in the second of them and backed off his throwing program. Team orthopedist Dr. David Altchek examined Santana earlier this spring, finding no structural damage in his arm.

"Not everything was there as far as my strength in my shoulder," said Santana, who recently sparred with Alderson over the state of his health. "At that point, we just talked about taking it easy and not trying to rush, and not trying to put a lot of stress on my shoulder, because it was not going to make any sense. And that's what we've been doing. But coming into Spring Training, I felt great. I was very excited about it. And then everything changed in a couple days."

These days, the Mets have little indication of when Santana might be ready. The team has already committed to Jon Niese as its Opening Day starter, with plans to slide Jeremy Hefner into the fifth spot of the rotation. Santana made 21 starts last season in his return from surgery; as recently as February, Mets leaders said they expected him to exceed 30 in 2013.

But that goal is quickly becoming unrealistic for Santana, who is not close to a return.

"I've been in this game for a while," Santana said. "I went through a lot a couple years ago and I'm still here. So I'm going to battle and try to come back and help as much as I can. But when that's going to happen, I don't really know."

Anthony DiComo is a reporter for MLB.com. Follow him on Twitter @AnthonyDicomo. This story was not subject to the approval of Major League Baseball or its clubs.