Johan Santana throws before the Mets' spring training game against...

Johan Santana throws before the Mets' spring training game against the Detroit Tigers in Port St. Lucie, Fla. (March 1, 2013) Credit: AP

PORT ST. LUCIE, Fla. -- There once had been optimism.

As recently as a few weeks ago, Johan Santana insisted to friends that despite a spring training filled with setbacks, he believed Opening Day was within his reach. But yesterday, reality reigned.

After Santana told reporters that he was unsure about when he might pitch again, Mets manager Terry Collins said it might take six weeks for the pitcher's ailing shoulder to be strong enough for a return to a big- league mound. General manager Sandy Alderson reiterated that a stint on the disabled list stint is "almost inevitable."

For the Mets lefthander, all signs point to an extended absence. Lefthander Jonathon Niese will start on Opening Day and righthander Jeremy Hefner appears most likely to take Santana's spot in the rotation.

"I've kind of had that feeling for a while," said Collins, who checks in daily with the veteran pitcher. "That he's going to be very cautious getting himself back, making sure his shoulder is at the same strength it was last year when he left here."

Collins may be setting a lofty goal for the two-time Cy Young Award winner, who is in the final season of a six-year, $137-million contract. The Mets still owe a guaranteed $31 million, which includes a $5.5-million buyout for the 2014 season. But the Mets may wind up paying for no production if Santana's fortunes don't turn.

"I went through [surgery] a couple of years ago and I'm still here," Santana said. "So I'm going to battle and try to come back and help as much as I can. When that is going to happen, I don't really know. All I know is I have to work and make sure that I get back into pitching."

Santana, 34, has spent most of the month long-tossing to rebuild strength in his surgically repaired left shoulder, though he's doing so at only 90 feet, or about half the distance required to even consider throwing off a mound.

"I'm making progress," Santana said. "It's just I don't know when I'm going to be pitching again. That's the thing: We cannot think ahead. The way we're approaching everything is every day, make sure we have a good day."

Since June 1, when he tossed the first no-hitter in franchise history, Santana has had few good days. Various physical maladies forced the Mets to shut him down in August. He followed with a winter of rest, hoping it would do his body good. Instead, the plan backfired, and team officials groused when Santana arrived in a weakened state.

An MRI exam revealed no new damage in Santana's surgically repaired shoulder, and an exam with team doctors reaffirmed the results. Nevertheless, Santana said Saturday that his shoulder still lacks the strength needed to pitch.

"The shoulder is not feeling good or it's just not strong," Santana said. "That's what I am doing right now, building up."

Santana has not appeared in a Grapefruit League game, and aside from what in essence was fielding practice, Santana hasn't thrown off a mound since March 3. That's when he threw an unplanned bullpen session in response to criticism about his health. Less than a week later, he shifted his focus toward building strength in his shoulder, a slow process that will drag on into the season.

Considering Santana's setbacks, Alderson said the most recent development came as little surprise.

"Not given what's happened over the last four or five weeks," Alderson said. "The situation has become more and more clear. He needs more time."

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