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2/22/2013 3:46 P.M. ET

Santana may not be ready for start of season

PORT ST. LUCIE, Fla. -- Terry Collins spotted it immediately while watching Johan Santana's bullpen session on Wednesday. The arm speed that made Santana a two-time Cy Young winner was no longer present. The signature bite on his changeup was gone.

A day later, Santana met with team orthopedist Dr. David Altchek, who diagnosed no structural damage in Santana's left shoulder but a general lack of strength. As a result, citing an "overall conditioning issue," the Mets have pushed Santana's throwing schedule back more than a week.

It could affect his status for Opening Day.

"It's obviously a possibility," general manager Sandy Alderson said of Santana relinquishing his April 1 assignment. "But right now we're still shooting for the opening of the season."

Because Santana did not throw off a mound in either Venezuela or Florida over the winter, preferring to maximize his period of rest, the Mets could not gauge his status until he arrived at camp last week. The left-hander climbed atop a mound Sunday for the first time since August, throwing 20 pitches without apparent issue. He then threw another bullpen session on Wednesday, demonstrating the lack of arm speed that concerned team officials.

"You could just tell," Collins said. "One of the things last year at this time that he really showed was that great feel for the changeup. He was trying to build up some velocity and he didn't have a real good feel for his release point. But at least he had the arm speed, and the other day I didn't see much arm speed."

Originally scheduled to make his Grapefruit League debut on March 2, Santana will instead long-toss at camp with the aim of debuting "somewhere in the March 10-15 range," according to Alderson. The left-hander proceeded on that track Friday, playing catch at up to 130 feet.

"I haven't gotten on the mound for a while so it takes time to get everything adjusted again, and to get in that pitching mode again," Santana said. "It takes time. That's what we're doing. It's not a setback at all. It needs time to build up."

When Santana first reported to Port St. Lucie, he told Alderson that he wanted to pitch in next month's World Baseball Classic. The Mets were not obligated to let him because he finished last season on the disabled list, and they exercised that right this week. Naturally disappointed, Santana said he understood.

The offshoot was that he no longer needed to rush his arm into game shape. Opening Day is still more than five weeks away, and even on his delayed program Santana can squeeze in as many as four Grapefruit League starts -- basically a full spring workload -- between now and then.

The only thing that could hold him back is health, but the Mets insist Santana is healthy.

"I think it was a matter of observation, and sort of a mutual recognition that maybe things needed to be backed off a little bit," Alderson said. "It's not a soreness thing. I wouldn't even call it a weakness. It's just where he is in his program is somewhat behind based on his winter and the injury last year, and his loss of the second half of the season."

In his long-awaited return from left shoulder surgery last year, Santana battled through an ankle injury, overall arm fatigue and an inflamed lower back, the latter injury ultimately forcing him to the DL. He proceeded with his regular conditioning program over the winter, but did not resume throwing off a mound until this week.

That put him further behind schedule than the Mets once anticipated -- though perhaps not to a damaging extent. Should Santana indeed make his Grapefruit League debut by the middle of the month, the Mets believe he can still build up enough arm strength to pitch on Opening Day.

It's just that his margin for error has thinned.

"This camp is about getting him ready," Collins said. "I'm worried about getting that shoulder ready. If we can get that, we'll be OK."

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.