PORTLAND – Justin Masterson was just looking for a second chance, and a sign.

He was in the second inning of his Major League debut on April 24 at Fenway Park, so the butterflies were gone. He’d just thrown a 1-0 change-up to Casey Kotchman, which the Angels’ first baseman crushed to right field, but foul.

Masterson looked in for the sign from Kevin Cash, wondering whether he should shake off the catcher if he didn’t call for the change-up again. He wanted to throw it again. He knew he’d mistakenly slowed his arm down for the first one and tipped Kotchman off that it was coming.

“I really knew I could throw a good one, keep the good arm speed,” the 23-year-old righthander said, “so I was hoping that Cashie would put it down and he did.

This time, Masterson maintained his regular arm speed, and Kotchman swung over the pitch.

“I threw it and you get that swing, and that’s what reinforces what you just did,” he said.

His brief stay in Boston reinforced a lot of things, Masterson said. Not just because he threw six innings of two-hit ball and would have had his first Major League victory if Boston’s bullpen hadn’t squandered the lead he left it to protect.

“Just being there showed that the well-executed pitches that I was making here in Double-A were well-executed pitches there, and coming back (to Portland) is just about executing those pitches again. It’s about being consistent and trying not to do more that what you do,” he said. “Just seeing how my slider played and how my change-up played just really showed that what I’ve been doing to make them better has been working.”

Observers agree that Masterson’s power stuff is already Major League-ready. Baseball America rated his fastball the best among Red Sox prospects, and his sinker is so heavy that some have suggested he is ideally suited for coming out of the bullpen.

The only thing that seems to keeping Masterson in a Portland Sea Dogs uniform right now is consistency with his secondary pitches.

“His slider and his change-up are significantly better from last year, and that was one of his goals that he set in his off-season,” Sea Dogs pitching coach Mike Cather said. “They’re actually much more improved that I would have expected.”

Masterson has struggled since his return from Fenway. He surrendered just two earned runs in his first four starts of the season before pitching in Boston. Including Saturday’s loss to Bowie, when he gave up five unearned runs in 4 2/3 innings, he is winless and has yielded eight earned runs in his three starts back.

Masterson confessed he’s been reluctant to admit to himself that the Boston start affected his focus, but now he thinks his big league experience, however brief, might have left such an impression on him that he’s been rushing to get back.

“When you get that taste and then you come back, I think you’ve got to pump the brakes a little and say ‘Hey, you’ve got to work for what you’ve got now and things will happen as they happen,'” he said.

Cather is confident that if another call-up happens later this season, as it has in years past with predecessors Jonathan Papelbon and Clay Buchholz, the Masterson that returns to Fenway will be even better than the one that made a big splash in April.

“His make-up’s off the charts. He’s confident. He’s disciplined. He know what he wants to do. He’s got everything that you need, and now it’s about putting it all together,” Cather said. “He is two years into the game and he’s got a really good feel on the approach. If you’ve got an approach, if you’ve got a plan and you are disciplined at your work, then you have the ability to get better at an exponential rate.””