Matt Barnes working on his repertoire for Red Sox

As long as he's been on the mound, Matt Barnes could count on his fastball.

It was his 95-mile-per-hour ace in the hole.

"It's been my go-to pitch," Barnes said. "It's what everything plays off of."

Between stints at Single A Greenville and Salem last season, he rang up 133 strikeouts. He was virtually unhittable in Greenville, where his ERA was 0.34.

In Salem, he threw 93 innings over 20 starts. He gave up more than eight hits per nine innings and his ERA jumped to 3.58.

He started thinking about the rest of his arsenal. His changeup was considered average, and the curveball, he said, was a struggle.

He didn't want to overthink it. But in the offseason, he thought about ways he could refine his repertoire.

Through six starts with Double A Portland this season, Barnes is 3-1. His 5.19 ERA doesn't reflect the work he's done nearly as much as his 31 strikeouts, but he's able to see the progress he's made on his secondary pitches.

"At the end of last year, I put a lot of emphasis on the changeup and really developing that pitch," he said. "Coming into spring training this year, my changeup, especially carrying over from last year, it's been a great weapon for me. I'm really comfortable with that.

"The curveball I struggled with a good amount last year, just trying to figure out what I was doing last year and overthinking things. In spring training, I switched the grip and the curveball's really become a good pitch for me. It's a pitch I have confidence with and that I can throw strikes with, get guys out with."

The expectations for Barnes were high. He was the 19th overall pick in 2011 out of the University of Connecticut. He spent his first professional season adjusting to new cities, new teams, new coaches. This year, though, there's a familiarity, particularly with Sea Dogs pitching coach Bob Kipper.

"There's a level of comfort and familiarity and it allows you to kind of open up and talk to those guys a little bit more and pick their brains a little bit more and just get the full level of their knowledge and maybe make suggestions about what you want to do," Barnes said. "It allows you to strictly focus on ways you can benefit."

Barnes goes into each start with a plan, but game situation dictates when Barnes can tinker.

"When we go out there and we're working on a pitch or we're trying to gain confidence on a pitch, we don't necessarily go out into the outing looking to just throw that pitch a certain number of times," Barnes said. "One game they may call for me to throw 15 changeups. The next game they may call for me to throw five. You kind of have to read swings of the batters and kind of take it within the game situation.

"You're looking for opportunities to throw it, but you're not throwing it for the sake of throwing it.

"So if a batter's late on my fastball two pitches in a row, just because I have him 0-2, I'm not going to throw a changeup just because I'm trying to work on it. It's throwing pitches based on what you see in the course of a game, situation in a game."

A couple of starts have gotten away from Barnes this season — he gave up five runs in 2⅓ innings against New Britain April 14 and six runs in 4⅔ innings against Trenton April 26. But in three of his last four starts he’s allowed one run or fewer over six innings. He’s also walked just nine over 26 innings this year.

"Obviously everybody loves to number-crunch, but it gets to a certain point in which you can't do that anymore," Barnes said. "You have to put all that aside and just really go out there and focus on trying to do what you're working on well.

"There's certain outings that pitchers are going to have where their numbers may not be great, but their numbers aren't indicative of how they threw. So it's one of those Catch-22s where if your numbers are great you know you're throwing [well] but your numbers may not be the best but you still feel great, you still feel like you're throwing really well."

Three to watch

Jayson Hernandez: The Greenville catcher entered Thursday hitting .356 (16 for 45). He falls short of qualifying among the South Atlantic League batting leaders.

Tony Thomas: After struggling in the early going, the Portland second baseman leads the Eastern League with 19 extra-base hits. He finished a home run shy of the cycle in a 10-4 win over Reading on Wednesday. He went 4 for 4 with two doubles and a triple.

Ryan Lavarnway: Since being optioned back to Pawtucket April 28, the catcher is hitting .313 (10 for 32). He went 2 for 5 with two RBIs in a 14-9 win over Gwinnett on Thursday.

Kaminska retires

After playing for three organizations over seven minor league seasons, Salem righthander Kyle Kaminska announced his retirement. Drafted by the Marlins in the 25th round of the 2007 draft, the 24-year-old started this season in Portland, giving up 19 earned runs over four starts before being sent to Salem, where he made two starts . . . PawSox third baseman Drew Sutton was placed on the disabled list May 3 with a side strain . . . Portland reliever Chris Martin is working on a scoreless streak of 19⅔ innings, the team’s longest since 2010.