LAKELAND, Fla. — Forget Opening Day. When Johan Santana climbs a bullpen mound Sunday morning for his most crucial throwing session to date, the Mets' season could hang in the balance, depending on the condition of his troublesome left elbow.

Santana already has been scratched twice from his scheduled starts after experiencing tightness in the triceps tendon in the back of the elbow. When he arrived on Saturday, Santana was ushered in to an 8 a.m. EST meeting with general manager Omar Minaya and manager Jerry Manuel that lasted roughly 40 minutes, though Manuel ducked out early to board the waiting bus for Lakeland.

The plan now is for Santana to throw a "light" bullpen session Sunday, then wait to see how he recovers in the next 24 hours before plotting a course back into the rotation. Even if Santana gets the green light, it could be as long as two weeks before he is allowed to make his Grapefruit League debut, and that could put his Opening Day start in jeopardy.

"We have 162 games and everything starts April 6," Santana said. "Is it going to be me or somebody else? It's tough to say right now. But as of right now, on paper, I'm supposed to be the one. But we've got to wait five more weeks to know that."

Santana, who was bumped from Friday's start against Team Italy, said he still feels tightness in the back of the elbow. The only reason for optimism is that he still is in Florida, not in an MRI tube in Manhattan.

That thinking could change quickly, however, if Santana has any problems Sunday. In that case, the two-time Cy Young winner will be on a LaGuardia-bound plane in a blink.

Minaya said Santana will be evaluated by the medical staff after Sunday's session and did not rule out a trip back to New York.

As for Manuel, he still is keeping his fingers crossed that Santana can be ready for Opening Day in Cincinnati. But the manager thinks it is more important that Santana at least be prepared to take a turn in the rotation during that first week.

"That's do-able," Manuel said, "because what we have to understand is that we still want the amount of starts. When we start affecting the amount of starts, then we've got an issue. We can do things here that will definitely affect that, and that's what I'm guarding against."

In Manuel's words, the Mets will be "extra, extra, extra cautious" with Santana, who has a relatively clean medical history. Santana spent 3 › months on the disabled list with a torn flexor muscle in 2001 and experienced elbow tightness toward the end of the 2007 season with the Twins before signing a six-year, $137.5-million contract with the Mets.

Santana showed no sign of trouble last season, even when he pitched the entire month of September with a torn meniscus in his left knee. He finished 16-7 with a league-best 2.53 ERA and totaled a career-high 234°innings en route to placing third in the Cy Young balloting. That workload and his rehab from Oct. 1 knee surgery were contributing factors in Manuel's decision to shut him down.

"You know Johan pitched a lot for us last year," Manuel said. "I pushed him a little bit last year. This is my opportunity to make sure everything is all right. I'm not concerned about March 1, March 8, March 15 — I'm concerned about April 6."

Santana appeared to be on pace for that assignment after showing up early Feb. 8 and stacking up bullpen sessions every other day. That accelerated throwing program could have put too much stress on the elbow, and now he'll have to make up for lost time — if there are no setbacks.

Santana estimated that he will need two or three sessions of facing hitters in live batting practice; that could push his first Grapefruit League start to the second week of March. Ideally, Santana will need four starts to get his pitch total up to 80, and then one tune-up for the regular season. Under that scenario, the latest Santana can make a start down here is March 12 to be on turn for Opening Day.

"We're just going to wait," Santana said. "Jerry will make a decision when I have to pitch again. In the meantime, I'm going to try to get myself ready, and he doesn't want me to put myself in any situation where it gets any worse."