FORT MYERS, Fla. -- In a sense, Justin Masterson's role for 2009 is yet to be determined. But in another sense, the Red Sox know exactly what they have in the young yet poised right-hander, who induces outs no matter which portion of the game he pitches in.

The beauty of Masterson from Boston's viewpoint is that he's thoroughly unfazed by being in limbo during Spring Training.

Putting on his starter's hat for Sunday's game at City of Palms Park against the Tampa Bay Rays, Masterson breezed through three scoreless innings, allowing a hit, walking none and striking out three.

"It's just great to be out on that mound, especially on the beautiful mound we've got here," said Masterson. "Right now, in Spring Training, for me to know either way is not going to change how I pitch. For me, I'm going to go out there and continue to work on throwing strikes -- getting a good feel for all my pitches -- and whether I'm starting or relieving, I need to have that either way. I'm just trying to get my body acclimated and ready to go. Whatever position we take after that, it will just be a matter of, 'let's go.'"

Heading into Spring Training, it seemed fairly certain that Masterson -- who turns 24 on March 22 -- would open the year as a reliever, a role he thrived in during the second half of 2008 and into the postseason.

But now that Brad Penny's throwing program has been slowed a little bit, there's a chance that, at least for part of April, the Red Sox will need a fifth starter.

Masterson is a wild card of sorts for Red Sox manager Terry Francona, who can simply put the righty in whatever role he fills best at a given time.

"Everybody has their opinions on where his ceiling is or how he can best help a ballclub," Francona said. "Some of that is probably going to be determined by the health of other pitchers and our needs, because he can serve in both capacities."

Not only that, but Masterson enjoys both capacities. A starter for basically his whole life until the Red Sox converted him into the bullpen last season in the heat of the pennant race, Masterson quickly fell in love with the adrenaline that comes with that role.

Now that he's starting again -- at least during Spring Training -- Masterson is loving that, too.

"When you're not doing it, you don't really think about it," Masterson said of starting games. "Now that I'm back in the starting role and getting three innings and kind of as we continue to get more, it's just different. You can't just let it out for one [inning], you've got to carry it over and we're continuing to see guys. So it's definitely a challenge within itself, which is what makes the game so great. If you're not going to be challenged, I don't think you're going to have that much fun."

Because there is the possibility of starting, Masterson is working on his changeup this spring.

"He could start or relieve and he's obviously done both, and if he does start, he can always go [back to relief]," Francona said. "The only thing it probably does is help. The more innings he pitches without being over-used, the more he learns how to pitch and the more he probably learns how to use his changeup. Last year, he went to the bullpen and he was basically a two-pitch pitcher out of necessity. If he starts, you're going to see him be a three-pitch pitcher, which would certainly help his development."

While Masterson's success last year was instant, there is a book out on him now. In other words, Masterson is likely going to have to take it up notch to have the same type of success.

"It's a little harder when you're not an unknown," Francona said. "And he certainly won't be. That doesn't mean he's not going to have a great year. But that's always the next jump. When you come in and you're the kind of guy that, I don't want to say, has nothing to lose, and then coming in the next year when there is a lot of responsibility placed on you, then you really find out how good guys are. I think that's probably part of the reason we're excited about him because we think he's going to be really good. But that's the next step."

As for role definition, Francona will let the situation play itself out for the next few weeks.

"We're fortunate," Francona said. "He doesn't lose sleep over it, so we don't lose sleep over it. We just know we have a pretty good pitcher. We'll get it all sifted out. There's just no reason to make decisions before you're supposed to or there's a chance the decision is going to be wrong. We'd rather not do that."