Mark Prior's pitching transformation

Prior, who struck out 245 batters in 2003, is on the verge of returning to the majors as a reliever. Mike Janes/Four Seam Images/AP Images

PAWTUCKET, R.I. -- The last vivid image of a healthy and strong and sturdy Mark Prior is nine seasons, two shoulder surgeries and an assortment of random injuries removed from now. He was in Chicago then, pitching in October and pushing the Cubs through the 2003 postseason, a 23-year-old arm trying to finish what generations of pitchers never could: pitch the Cubs to a World Series.

And Prior, with help from Kerry Wood and Carlos Zambrano and others, got them close. But then a ball went down the left-field line and things were never the same for the Cubs. Things were never the same for Prior, either.

"Yeah, I'm not the pitcher now at 31 that I was," Prior admitted.

This is the obvious part. Prior has experienced a lot of life since being drafted No. 2 overall in 2001 out of USC. He's seen his career rise, he's seen it crash. He's been an All-Star and a Cy Young candidate. He got married, had children, bounced around operating rooms.

And so it's somewhat striking to see Prior now, sitting here in shorts and a Red Sox top, smiling and clean shaven, looking so young. He has a fresh lather from some aerobic work. He looks strong.

"People like to talk about the velocity because it's not the same," Prior said. "But I'm not that far off. It doesn't mean I still can't be good."

The doubts that Prior can be good aren't as prevalent as the doubts that he can be healthy. But if he does remain healthy -- he recently visited the seven-day DL with a strained oblique -- what's left? After all these broken years, what can Prior offer the Boston Red Sox?

So far, Prior has been stellar as a reliever for Triple-A Pawtucket, striking out 27 in 13 1/3 innings with a 4.05 ERA. But there's a six-year gap that remains relatively unanswered for. Since Aug. 10, 2006, which is the last time Prior appeared on a major league mound, he pitched just 24 innings of professional baseball before joining the PawSox, and that includes 11 innings with the Orange County Flyers -- an independent league team based in California -- in 2010. And when Prior joined the Orange County Flyers, the residual effects of his shoulder operations were apparent.

"His first live BP, he was 87 to 89 [mph]," said Paul Abbott, Prior's manager in Orange County and now the pitching coach at Boston's Class A Short-Season Lowell affiliate. "What happens with shoulder surgeries is you get a little passive and afraid to let it go. You're just worrying about your arm. I wanted him to use his legs more and not worry about his arm."

Prior's velocity increased with the Flyers as his arm strength did. He pitched at 89-93 mph, about where he's been this season. But nobody really knew it would work this way, that the fastball would rip through the zone in the 90s and hit both corners and miss bats. The two years separating Orange County and Pawtucket weren't healthy ones.

"We knew what arm he used to have, but we didn't know now," Pawtucket manager Arnie Beyeler said. "There's a reason he was not in the big leagues."

Prior's fastball isn't exploding in the mid-90s the way it once did, but it's still plenty good, especially when he commands it to both sides. He still uses it about 70 percent of the time, still attacks with it, still trusts his innate feel more than the radar gun.

"I read what the hitter is telling me," Prior said. "If they're not on [the fastball], I'll keep throwing it."

It's hard to anticipate how major league hitters will react to Prior's fastball, but velocity is only one component. Prior -- a 6-foot-5, 230-pound right-hander -- has always had a mystical "heaviness" to his heater, the inexplicable nature that makes a baseball feel weighted when it pops the mitt. Hitters don't like this.

And he's always had some deception in that compact delivery fit for a phone booth, in which he gathers over the rubber and drives directly to the plate, the ball hidden behind his head. That everything arrives from the same three-quarters arm slot adds to the deception.

"His fastball seems harder because you don't see it until it's halfway to the plate," Pawtucket catcher Ryan Lavarnway said.

Mechanically, Prior is very much the young kid in a Cubs uniform. He's made miniscule tweaks -- shortened his arm swing a touch, slightly raised his arm slot -- but nothing, he said, the naked eye would notice.

"The big thing is I don't want him to drop his elbow," Pawtucket pitching coach Rich Sauveur said. "He does that a lot, and that's where he loses command. I remind him of it all the time. When his fastball misses up, it's because he has a low-elbow delivery."

If there's been one blotch on Prior's record since joining Pawtucket, it's command; he's walked 15 men, which is roughly one per inning, so he jots mechanical notes down. He started that a few years ago, keeping notes on the good days and the bad. He wants to remember what felt good and what didn't.

"When you get hurt and sit around for five months, you forget some things," Prior said.

Perhaps the biggest tangible difference between the younger and healthy Prior and the older and healing Prior comes in his secondary offerings, and even those changes emerged more from circumstance than calculation. His breaking ball now resembles a 12-6 curveball more than a hard, slurvey hammer. He's slightly moved a finger on the ball, but he didn't initiate the pitch's transformation.

"Those things change because of age and surgery," Prior said with an "it happens" shrug.

Prior's third pitch, a circle changeup, gets neglected now as a reliever. In extended spring training, he tried a splitter but ditched it because it wasn't time for experimentation, but time to get game-ready. It was time to pitch and see what he could be in Boston. Prior is adamant that he aspires to be only an effective big league pitcher again, that he doesn't have benchmarks for success like he did years ago.

"The older I've gotten, my perspective of success and failure has changed," Prior said. "People want to make it a black-and-white thing, but you can't always do that. Now, it's about getting a hitter out, getting out of a [jam], those little victories. Keep lining up those little victories."

Beyeler said Prior is probably best suited for a one- or two-inning role to avoid further durability questions. Sauveur thinks Prior could be valuable as a long man. Whatever the role, his future is as a reliever, a Red Sox official said. Boston wants to see continued success and, of course, continued health. And then Prior will get a look. "His ability to pound the zone and get swings and misses could help the 'pen," the official said.

For a man who was once elevated so highly by the arms of great expectation, Prior seems to have found a compromise between accepting diminished dreams and being comfortable with the reality that there are hardly any expectations now.

"I don't want to say I'll never be the guy that I was," Prior said, trailing off.

He doesn't finish that thought, probably because he already knows it's unlikely. He's still talented enough and young enough to have a quality career ahead of him -- he knows this. But he also knows questions about his health will follow him to Boston, to retirement.

He's probably not capable of the lofty dreams he had a decade ago.

Prior seems content with this because he wholeheartedly and confidently believes in his ability to produce little victories, and those will do.

Teddy Mitrosilis is an editor for ESPN Insider. He played college baseball at Long Beach (Calif.) CC and the University of North Carolina at Chapel Hill, where he graduated with a degree in journalism. You can follow him on Twitter here.