PORT ST. LUCIE, Fla. -- As his teammates trickled back into the clubhouse following Wednesday's workout, Reese Havens sat quietly in front of his locker. Havens had not participated in the morning's activities. He had not participated the day before, either. Havens hopes to rejoin his teammates on the field soon, but he is not quite sure if he will be able to do so.

Such is life for Havens, a second-base prospect drafted four spots after Ike Davis in the first round in 2008. The Mets have been holding Havens out of workouts due to a stiff back, the same trouble area that forced him to the disabled list last season, part of a rash of core injuries that have undermined his career.

"It's been embarrassing," Havens said earlier this week. "Everybody has expectations for me, none higher than my own."

He completed that thought by noting that "it's also part of the past." But the following morning, Havens alerted manager Terry Collins to his most recent bout of back stiffness, skipping daily workouts for the first time this spring.

About a week earlier, Collins had identified Havens as the player he was most looking forward to watching in camp. By Wednesday, that talk had changed, with Collins calling Havens "about as down as I've seen him."

"He's got a chance to play and show everybody what he can do," Collins said. "And he will. We know he's going to be out there. But to have this happen at this time, he's real frustrated and so are we."

"He's just been riddled by injuries, man," said Davis, who roomed with Havens and trained with him at the Fischer Sports rehabilitation center in Arizona over the offseason. "That's why this game is so tough."

Some might say the game is tough due to baseballs hurtling toward home plate at high velocities from close range. But Havens seems to have mastered that part of it, hitting 15 home runs in 345 at-bats since 2010 while reaching base nearly 38 percent of the time. In comparison, only Davis, Carlos Beltran and Jose Reyes posted such high on-base percentages for the Mets last season.

"It's been pretty impressive, right?" Mets farm director Adam Wogan said. "Hopefully that continues over a longer span of time."

But at some point, the Mets have to wonder. After leg and wrist injuries sidelined Havens often during his first professional season, problems with his core began limiting him in 2010. Following that summer -- one in which he played in just 32 games -- Havens underwent surgery to shave an inch off one of his ribs; the procedure aimed to eliminate the abdominal pain that Havens had been experiencing due to bone movement in his midsection.

A winter of rehab guided Havens into 2011, but did not prevent him from missing two more blocks of games due to abdomen and back issues. And now this latest bout of stiffness.

"Lower-back injuries are some of the most debilitating injuries in all of occupational medicine, regardless of whether you're an athlete or whether you're a plumber," said Mike McKenney, the trainer who worked most closely with Havens at Fischer Sports this winter. "What's difficult is that [baseball players] push their bodies to a very high level. These guys, they're not just sitting at a desk. They're swinging a bat about as violently as they possibly can."

After running Havens through a diagnostic test this winter to seek out any physical dysfunction or predisposition to injury, McKenney and his colleagues settled on a personalized program for Havens. The aim was to increase the second baseman's hip and upper-back flexibility, while also developing his core strength.

Heavy on sport-specific drills and baseball activities, the program allowed Havens to work alongside Davis and others on the field and in the batting cage. The goal was not only to improve his physical condition, but also to develop enough strength for him to maintain it over a long, trying season.

"He didn't want to take this year for granted," McKenney said. "He wanted to put his best effort forward to remain healthy. Because if he's healthy, he knows he can play at the big league level."

"It's like a stress relief for us, getting on the field," Davis said. "When you don't have that, and all you do is go from the training room to the hotel back to the training room, it's not a good feeling."

Adding to Havens' frustration is the fact that so much opportunity exists in New York for players with his skill set. Though the Mets are banking on the offensive-minded Daniel Murphy to hold down second base this season, Murphy is hardly a lock to do so. The organization is likewise enamored with Ruben Tejada's defense at shortstop, but unconvinced of the 22-year-old's ability to hit.

That uncertainty has left plenty of room for older prospects such as Havens -- he'll be 25 this season -- and Jordany Valdespin to push their way into the middle-infield conversation.

"Of course I've thought about it," Havens said. "That's the position I play. I know there's a good opportunity there and I just want to have the right mindset to better myself and put myself in a good position for that job."

That means staying healthy and continuing to hit -- though the latter has never been an issue.

"I've dealt with it for three years now," Havens said of his lingering health issues. "I just want to go out there and play."