He returned to Portland to start this season, then ended it in style in the same spot on Saturday night.
The Red Sox's No. 15 prospect allowed one hit over six shutout innings to help the Sea Dogs top Reading, 6-1.
Pimentel fanned six, walked two and threw 52 of 78 pitches for strikes. He finished the year 6-7 with a 4.59 ERA and 86 strikeouts over 115 2/3 innings.
The reason for his latest success was simple.
"You know, it's all about command in everything you do," Pimentel said. "The fastball, the changeup, the slider -- all of them I was able to throw for strikes. When you can be in that strike zone and don't get behind in the count, you make things much easier."
All of this coming from a 22-year-old right-hander who was 0-9 with a 9.12 ERA at Double-A last season. Beyond being given a year to develop physically, the key to Pimentel's 2012 turnaround has been between the ears.
"He struggled processing failure a year ago and we just don't see that anymore," Sea Dogs pitching coach Bob Kipper said. "That speaks to the mental toughness he's developed. He's learned to kind of push through any hiccups he does have, and that's helped him get significantly much more confident."
Pimentel agreed with that assessment.
"Everything is about your confidence," he said. "I wasn't really confident with all my pitches last year, and that hurt me. This year, I had that confidence. I could throw my stuff whenever I wanted, and that really helped.
"I learned from last year not to be worried about the small stuff. If I give up a base hit or a walk, don't worry about it and just pitch to the next batter. I started focusing more pitch-by-pitch, batter-by-batter."
That mentality was on display in the third inning Saturday.
Miguel Abreu led off with a single and became the first Phillie to get in scoring position when Troy Hanzawa sacrificed. The 2011 version of Pimentel might have become overly concerned about the situation before him. The 2012 edition? He needed seven pitches to strike out Tyson Gillies and Cody Asche.
The native of the Dominican Republic retired eight in a row after the pair of punchouts before walking a batter in the sixth.
With the Sea Dogs' season ending Monday, the win was Pimentel's last of 2012. He went 2-2 with a 2.97 ERA in his final six starts, a far cry from last year and the 5.84 ERA he put up in 12 starts in the first half of this season.
With the offseason looming, Pimentel plans on returning home, where he will continue to fine-tune his mechanics and his arsenal to the point where starts like Saturday's are more commonplace.
"I'm not one of those guys who's really into projecting whether a guy will be a No. 1, 2, 3, 4, 5 or bullpen pitcher," Kipper said. "But I know this guy has got a chance to make a real impact, to be really solid in the Major Leagues."
Pimentel outpitched Trevor May, the Phillies' top prospect, who allowed four runs on six hits in four innings.
Zach Gentile led the Sea Dogs' offense, going 3-for-4 with a double, three RBIs and two runs scored out of the ninth spot in the order. Jackie Bradley, Boston's No. 6 prospect, left after apparently aggravating an ankle injury in the third inning. He was replaced by Ronald Bermudez, who went 3-for-3 with a double and three RBIs.