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Stolmy Pimentel is as hard to predict as the New England weather. A right-handed pitching prospect in the Red Sox organization, Pimentel has shown an ability to dominate—twice last year he carried no-hitters through six innings—while at other times he has been frustratingly hittable. His Jekyll-and-Hyde performances are reflected in the rankings, as despite his high ceiling, Kevin Goldstein rates him as just the 10th-best prospect in the Boston system. Baseball America and Keith Law are somewhat more bullish, each placing him at number six.

A native of San Cristobal in the Dominican Republic, Pimentel has flashed ample promise since signing as an international free agent. In 2007, he was named the Red Sox Minor League Latin Program Pitcher of the Year. In 2008, he was named a New York-Penn League All-Star, and last summer he pitched in the Futures Game. In each of his three professional seasons on American soil, he has been young for his level, making his numbers more impressive than they appear on the surface:

2008: 5-2, 3.14 ERA in short-season Lowell as an 18-year-old.
2009: 10-7, 3.82 ERA in Low-A Greenville as a 19-year-old.
2010: 9-11, 4.06 ERA in High-A Salem as a 20-year-old.

Pimentel’s repertoire includes a four-seam fastball that tops out at 95 mph, a two-seam fastball that is in the development stage, an above-average 12-6 curveball, and a changeup that rates as the best in the Red Sox minor-league system. He also has a good pitcher’s build—Pimentel is listed at 6-foot-3, 185 lbs, but appears to be bigger than that—so the framework for big-league success is there. The problem has been consistency.

While it is common for young players to experience ups and downs, Pimentel’s peaks and valleys have been especially pronounced, especially given his potential to become a front-line starter. An American League scout who saw him several times last summer was left shaking his head after repeatedly seeing both extremes.

“He’s been a different guy every time,” said the scout. “One game he has good velocity and the next game he’s a few ticks slower. The same with his breaking ball. One day it’s sharp and the next time it’s not. When everything is working, there’s a lot to like, but I’ve seen a lot of inconsistency and it’s hard to say exactly why. He doesn’t look all that different from game to game, but his stuff does.”

Asked about the scout’s comments, Pimentel didn’t disagree. To his credit, he instead addressed the issue head-on, emphasizing the need to improve.

“Yes, I think he might be [correct],” said Pimentel. “Sometimes when you’re pitching, your fastball is not working. The same with your secondary pitches, like your changeup or your curveball. When one isn’t working, I think that you have to use the other pitches that you have. You can’t be like, ‘Oh my god, my changeup is not working.’ What you have to do is keep pitching and try to be consistent with your pitches.

“When you're not [pitching well], you have to try to do what you haven’t been doing,” continued Pimentel. “You want better command, so you refocus and try to pound the strike zone. The most important things for a pitcher are to pound the strike zone and be consistent.

“If you can’t fix it yourself, you need to get help, because you don’t know everything and maybe somebody can help you. Sometimes they tell me I’m trying to throw too hard and opening up too much. I listen. I try to stay positive and keep working to be more consistent.”

Mike Hazen, Boston’s director of player development, was also asked about the scout’s assessment. His response was similar to Pimentel’s, although he opted to speak in generalities rather than address the young right-hander specifically.

“You can see a different 20-year-old any time out there,” said Hazen. “When we talk about [a player’s] consistency, that’s what we mean. One day they come out there throwing 94-95 [mph] with a good curveball and a changeup, and the next time out—and this happens at the big-league level, too—they don’t have their changeup and they’re throwing 91-92 with a little less command. The big-league guys know how to manage that; they know how to get through that game. For a minor-league player, it’s a little more difficult.

“It could be mechanics, repeating their delivery, or something they’re working on, but it might not be,” continued Hazen. “Maybe they didn’t sleep right the night before and don’t know how to cope with that yet. Or maybe the strike zone is smaller, so they get frustrated in the first inning. There are a myriad of factors and that’s why the minor leagues exist. These guys have to go through that progression in order to get up to [a higher] level of baseball where they have to have that consistency day in and day out. A big leaguer might be executing eight or nine times out of 10, and a minor leaguer only six, which isn’t good enough up here. It’s good enough down there, as long as they’re continuing to show improvement.”

According to Anthony Rizzo, who went to the Padres this winter in the Adrian Gonzalez deal, his former teammate has the makeup—and the dominant pitch—to go far.

“Stolmy has a great changeup,” said Rizzo, “but what stands out just as much is his demeanor. He’s in control of the game and doesn’t really get rattled if he gets hit around a little bit. If he was giving up 10 runs in an inning, he’d still be the same guy. I was pretty impressed with Stolmy.”

If he develops the consistency that has thus far eluded him, Pimentel stands an excellent chance of one day bringing his signature pitch to Boston. According to a scout for an American League team [not the one who was referenced earlier], the tantalizing change-of-pace will play a big role in getting him there.

“There is very little difference in arm speed between his fastball and his changeup,” said the scout. “There is a lot of deception because of that, and his changeup can be a plus pitch for him in the big leagues. I think he has a good chance to get there, I really do. He hasn’t been good every time I’ve seen him, but when he has been, he’s been very good.”

Pimentel, who participated in Boston’s rookie development program in January, is expected to begin the 2011 season in the starting rotation at Double-A Portland.

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Excellent portrait of the pitcher as a young man. The interview skills you've developed are put into real service on this evaluation. More, more...