BRADENTON, Fla. — Pirates Twitter was abuzz over Tyler Glasnow’s Grapefruit League start Sunday against the Red Sox at LECOM Park, although the hubbub wasn’t so much about his pitching line as his repertoire.

To get to the point: Was Glasnow mixing in a cut fastball?

He’s never thrown one in his major-league career, as far as pitch-tracking technology can tell, but there was discernible glove-side movement on several of Glasnow’s fastballs while he navigated 4 2/3 innings of one-run ball in Boston’s 2-1 win.

That fact, combined with the fact that Glasnow’s fastball velocity occasionally dropped into the low 90s led many fans on social media to speculate that he was putting a new pitch into play while also trying to put his best foot forward before opening day.

However, Glasnow categorically denied that there was anything different about his performance from a pitch-mix standpoint. First, he addressed the movement.

“My fastball cuts, usually,” he said. “Thirty percent of the time, 40 percent of the time, it has a natural cut to it, so that’s always kinda … that’s how I’ve always pitched.”

Second, he shrugged off the variance in speed as unintentional.

“That’s just going down the mound a little quick,” Glasnow explained. “It gets ‘behind’ me.”

Take Glasnow’s words at face value, or don’t. Maybe it’s simply a matter of semantics. If a fastball has a cutting action, is it really a ‘cutter?’

Regardless, he kept a Red Sox lineup off-balance with better control command than we’re accustomed to seeing from him. Six strikeouts and two walks would indicate his accuracy was improved, but Glasnow credited a pregame directive from Ray Searage to establish the inside fastball for much of his success.

“I didn’t do that my first couple of outings,” Glasnow said, referring to his 11.74 ERA in 7 2/3 exhibition innings prior to this. “Just get ahead and show I can get it in there. Had a lot of uncomfortable at-bats today.”

Sounds a lot like what Jameson Taillon said Friday, so perhaps we have a theme developing. Not only are Pirates pitchers aiming to change hitters’ ‘eye level’ vertically, they want to reinforce the importance of pitching inside.

“As long as he hits (the inside corner) it opens up everything for him,” Clint Hurdle said. “If you don’t hit it, you’re behind in the count. One of the next steps for him is to get ahead in counts and put hitters away when he’s ahead in counts.”

Glasnow still sprayed several fastballs — and a few curveballs — in his fourth spring start, but righty hitters Xander Bogaerts and Rusney Castillo seemed especially unsettled when in the box. Which was the point.

“For a guy like me, who (doesn’t have) super pinpoint control, it definitely puts a little fear in the batter, not knowing where it’s gonna go,” Glasnow said. “My first few outings, I was really only going away and throwing the curveball, so (the hitter’s) shoulder would leak (over the plate) and anything over the plate was easy to hit. So, going in there and opening them up opens up both sides of the plate to me, so I kinda get away with a little bit more.”

So there you have it. The challenge will be for Glasnow to have decent enough control to make hitters acknowledge the possibility he might burn them with an inside strike. If a little bit of movement helps him burrow that ball on the inner half, all the better.

The Red Sox made Glasnow pay for loose command late in the outing, stinging a few balls to the deep reaches of the outfield. Mookie Betts just missed a home run to left in the fifth, settling for an RBI double. All of it illustrates the progress the towering righty still has to make with consistency.

But at least he’s capable of generating outings like Sunday’s, against a Boston lineup that was at about 50 percent of regular-season strength. It’s still just exhibition play, but the flinching reactions his pitches inspired from hitters were real.

“I really liked the way he attacked the hitters today,” Hurdle said. “Elite pitchers can go in for strikes, go in off the plate and move people when they have to. That’s one of the parts that developing for Tyler.”

At this point of the spring, even with Joe Musgrove (shoulder) on a delayed build-up schedule, Glasnow’s only hope to join his mates in Detroit for opening day will be in a long relief role. Considering his struggles in the majors to date, that’s not an assignment he’s in a position to protest.

“Whatever they want me to do,” he said, “I’ll do it.”

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