JUPITER, Fla. -- Statistics are one thing. Anecdotal proof of Johan Santana's sharpness came in the middle innings Wednesday, when Cardinals third baseman David Freese twice lost the grip on his bat while flailing and missing at Santana's offspeed pitches. First was a slider in the fourth inning, then a changeup in the sixth. In each instance, Freese's bat went flying into the stands.

"There are some minor steps, there are some baby steps and there are some giant steps," Mets manager Terry Collins said afterward. "And today was a giant step forward."

In addition to whiffing six batters in six innings, Santana held a lineup full of Cardinals regulars to six hits and a run in his longest outing to date. Though he was still not ready to declare himself ready for Opening Day after easily his best performance of the spring, Santana continued to express confidence that he is on the proper track.

"We're getting closer," the left-hander said. "Every time that I go through one day, I'm closer to coming back. I'm definitely working my way to be ready for Opening Day. We'll see how everything goes."

As he has after each of his four Grapefruit League outings, Santana indicated that a more significant test will come in two days, when he attempts to throw his routine between-starts bullpen session. If he feels no pain in his surgically repaired left shoulder, he will remain on track to pitch again on Monday against the Cardinals.

So far, Santana has felt nothing even remotely abnormal in his shoulder as his pitch count continues to climb. Wednesday's outing saw him throw 48 of his 69 pitches for strikes, a far better ratio than earlier in the spring. And he did it while maintaining his velocity in the upper 80s, jumping above 90 miles per hour on occasion.

If all continues to go according to plan, Santana will pitch again Monday before making his final spring outing -- likely an abbreviated one -- on March 31. Then he will take the mound at Citi Field on April 5, pitching in a regular season Major League game for the first time since Sept. 2, 2010.

"Obviously we're very optimistic about the way he's worked so hard," Collins said. "He's never missed a beat. He's done exactly what he's been asked to do."

Bay's willingness to play center opens options

JUPITER, Fla. -- To be clear: Jason Bay is not volunteering to be an everyday center fielder.

"I'm not suited for that," Bay said.

But if both Andres Torres and Scott Hairston are not healthy enough to start the season, Bay is happy to sub at center for a few days, a week, whatever.

"I don't know if I'm going to be the best center fielder in the league," he said. "But if it gives us a chance to get other guys in certain spots, I feel I can do it."

If nothing else, Bay's flexibility may give the Mets more options as they wait to see how Torres and Hairston heal from their injuries. The team had no update Wednesday on Torres, who strained his left calf in Tuesday night's game and remains day to day. Nor can they speculate upon a return for Hairston, who has struggled to recover from a strained left oblique.

That uncertainty has led Mets manager Terry Collins to consider some unorthodox ideas for the position, from shifting Bay to center to trying out infield prospect Jordany Valdespin in the outfield. The latter may be the most intriguing possibility, considering Valdespin's .333 average and .533 slugging percentage so far this spring, as well as his overall athleticism. But he has never played there as a professional, creating some wiggle room for more experienced competitors Mike Baxter and Adam Loewen.

Valdespin, for his part, has jumped at the opportunity to learn a new position, given the glut of infielders already ahead of him on the depth chart.

"I want to play in the big leagues no matter where I play," said Valdespin, who spent time practicing in the outfield over the winter. "If I stay in the big leagues I can help the team."

Twisted ankle sidelines prospect Wheeler

JUPITER, Fla. -- The Mets' ever-growing injury list apparently does not discriminate against Minor League players. Top pitching prospect Zack Wheeler turned his left ankle walking up the steps to his apartment last weekend, and will not make his next start in Minor League camp.

"The ankle is fine everybody," Wheeler tweeted after the Mets announced his injury. "It's nothing serious. I threw on it today. And we are just taking it easy. It's Spring Training. Still early."

No. 1 on MLB.com's list of the Mets' Top 20 Prospects, Wheeler did not join older and more experienced pitching prospects Matt Harvey and Jeurys Familia in big league camp this spring. But at least prior to his injury, he did stand a good chance of starting the season alongside those two at Double-A Binghamton.

Whether an extended absence might change that is nothing more than speculation for now. No matter what, the Mets will proceed cautiously with the 21-year-old Wheeler, who allowed a total of six runs in six starts after the Mets acquired him from San Francisco last summer.