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03/08/12 5:37 PM EST

So far, so good for Johan after bullpen session

Still pain free, recovering Mets ace taking it one day at a time

PORT ST. LUCIE, Fla. -- Done warming his valuable left arm on a side field Thursday morning, Johan Santana began walking toward a bullpen mound when he spotted one of his agents, who also represents former teammate Jose Reyes, leaning against a nearby chain-link fence.

"I just want you to know that I've got something for Jose," Santana called out to him, grinning. "He's going to get a good look at it, but he's not going to hit it."

This is the sort of good-natured banter that is becoming more commonplace for Santana, now that his confidence is growing by the day. The Mets considered Thursday's throwing session just as significant as Santana's start two days prior, knowing that the most vexing aspect of left shoulder rehabilitation can be bouncing back to full strength between outings.

Because of that, the Mets had been unsure if Santana would even throw a full bullpen session on Thursday, two days after making his first Major League start in 18 months. But the two-time Cy Young Award winner emerged from a side door of the clubhouse shortly after 11 a.m. ET, carrying his glove and spikes and walking briskly out to the field.

A few dozen harmless pitches later, Santana walked off the mound as healthy as he was at the start of the morning.

"For me, it's a day-to-day thing and every day is important," Santana said. "Every time that I [pitch] is a day closer to coming back."

More than control or command or even velocity, the most difficult thing for pitchers to establish following anterior capsule surgery is resiliency. Pitching well on a given day, as Santana did in his Grapefruit League debut against the Cardinals on Tuesday, is not the primary issue. Doing it every five days, without pause, is what the Mets need to see.

That is why manager Terry Collins and pitching coach Dan Warthen -- along with a slew of other coaches, trainers and even teammates -- gathered Thursday to watch Santana throw what would have been a routine bullpen session for any other pitcher. By this point, Santana is used to the spectacle; his throwing sessions have drawn sizeable crowds since he first arrived at camp. But this may have been the most significant one to date.

Assuming Santana wakes up this weekend feeling just as strong as he did Thursday, he will pitch against the Marlins on Sunday. Then he will repeat the trick five days later, and five days after that, all the way up to Opening Day. Between starts, he will throw more bullpen sessions like this one, with the Mets checking in to make sure everything is in place.

"He was pretty stiff [the day after his start], which you come to expect with the little extra adrenaline," Collins said. "I told him, 'It's going to be like that each time you go out there. The more you build up, the stiffer you're going to be.' But he feels fine."

"For me, it's a day-to-day thing and every day is important. Every time that I [pitch] is a day closer to coming back."
-- Johan Santana

Collins acknowledged that he is no longer hanging on Santana's every move, as the manager rightfully was at the start of Spring Training. Three weeks in, Collins has seen enough to feel comfortable that his ace will start Opening Day against the Braves, even if a hiccup or two happens to surface between now and then.

Santana's goal coming into Spring Training was to be just another pitcher. In that sense, at least, he already is.

"I think he's going to be healthy," Collins said.

Next up for Santana is a Sunday start against Reyes and the Marlins, in which the left-hander will throw three innings. After that, probably four innings. Then five. Then six.

Given that agenda, Santana is starting to talk about specific baseball issues now, such as incorporating his slider more frequently into his repertoire. No longer simply concerned about his health, Santana can afford to tweak based on how his arm feels. Control and command are the buzzwords now, more than mere survival.

To be clear: Santana is far from invincible, and he will always be a single pitch away from disaster. But the crowds surrounding his bullpen sessions are beginning to lessen, their members talking and fiddling with cell phones instead of hanging on every pitch.

Just another pitcher, it seems, is a good thing to be.

"We have worked hard," Santana said. "I'm getting back to where I used to be, so that's a good sign."

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.