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Over the course of the summer, the Pirates called up a litany of top prospects to the Majors, a list that includes Henry Davis, Endy Rodríguez, Liover Peguero and Quinn Priester. But it has been Jared Triolo who has quietly been Pittsburgh’s best rookie.

He’s hit for average (.273). He gets on base (.364). His defense is as good as advertised (five Outs Above Average), and he’s been an above-average baserunner (four steals). All that amounts to Triolo leading Pittsburgh’s rookies in bWAR (1.3). There’s only one area of his game in which he’s below average: slugging percentage (.360).

In recent days, the slugging has arrived in a hurry.

Over the last week-and-a-half, Triolo has slightly-yet-noticeably altered his batting stance in the pursuit of power, less of a change in mechanics and more of a change in set-up. The sample size is small, but the early returns are extremely encouraging.

“You start looking at the big picture for him,” hitting coach Andy Haines said. “When you look at how he’s made physically and how he’s wired, we thought, ‘Hey, he’s leaving a lot on the table here. How do we help get to that?’ You have to give Jared so much credit. The guy gets to the big leagues and he’s willing to jump right in there and go after it.”

Here’s Triolo on Sept. 9th, his first game since being recalled from Triple-A Indianapolis:

Here’s Triolo on Sept. 20th, the night he hit his second home run of the season:

In the first clip, Triolo is more crouched. In the second clip, Triolo is more upright. All other mechanics -- hand placement, stride -- remain constant.

Triolo assessed that he had gotten “a little bit lax” with his posture upon being recalled from Triple-A Indianapolis in early September. Haines, then, suggested a tweak. After sitting out on Sept. 15 and 16, Triolo returned to the lineup on Sept. 17 with a new stance in tow. That afternoon, Triolo roped a two doubles off left-hander Carlos Rodón, both of which just missed being home runs by a couple of feet.

Triolo assessed that the change has given him more time to see pitches and, in turn, swing at the right angles. Since making the change, he’s certainly been swinging at the right pitches. Triolo has reached base at least once in each of the last five games, totaling two homers, five walks and seven hits, raising his OPS from .618 to .724 in the process.

“Jared profiles as such a high-floor player,” Haines said. “It’s just a great place to start as a hitter. He has all the foundational attributes. He’s a hitter first. He can navigate an at-bat. With his physicality and his hardware, you know if he can keep learning more about himself and tap into who he is at his best, you know that when they make mistakes out over the plate, he can do what he’s done the last few games.”

“The big league game shows you if it works or not, so why wouldn’t you try it?” said manager Derek Shelton. “One of the great things about Tri is that he’s inquisitive, he’s smart, he asks good questions. It’s not just going to be a blind, ‘Hey, we’re going to do it.’ That’s the one fun part of being a hitting coach when you have those conversations. … The most important thing for him and Andy is that when you see the results, then you start to smile a little bit.”

For Haines, these tweaks won’t just allow Triolo to unlock more power, but allow him to be more effective with pitches on the outer third of the plate.

Despite Triolo’s wingspan, he’s handled pitches inside well thus far. On pitches middle-in, specifically, Triolo has a .571 batting average and .495 wOBA. Triolo’s home run against Hayden Wesneski on Wednesday at Wrigley Field was on a pitch that was up-and-in, a zone where Triolo has a .412 wOBA. When Triolo has to extend his arms, though, he’s been ineffective.

On pitches middle-out, he has a .229 wOBA. He's got a .176 wOBA on pitches up-and-out, and a .201 wOBA on pitches low-and-out. A quick glance at his heat map illustrates the contrast between Triolo’s hot and cold zones.

“He’s a hitter before the power,” Haines said. “But it was more about getting to the truth here: When he gets these mistakes up out over the plate, being a long-levered guy, he should be able to leverage that ball and do more damage when that happens. You also look at how much he covers the plate, the outer lane was kind of not available to him.

“When you look at that, being a long-levered guy, you kind of work backward and say that shouldn’t be the case. He should have plenty of coverage on the outer lane. It was more about, with him, getting to the best version of what we thought his hardware would allow him to be.”

If Triolo inches closer to that best version of himself, there’s a good chance he’ll find himself in the starting lineup more often than not.

Third base, Triolo’s position all throughout the Minors, is, of course, Ke’Bryan Hayes’ territory. That said, the Pirates don’t have a definitive starter at either first or second base going into next season. Triolo isn’t a natural first or second baseman, but he’s shown in a limited sample that he’s plenty capable. And as the adage goes, if Triolo can hit -- and hit for power -- they’ll find him a spot in the lineup.

“This guy is a difference maker for the Pirates if he keeps doing this,” Haines said. “He’s a tremendous defender. He’s a great baserunner. He has the other traits as an offensive player. Now, if you get him to the place where he can damage some mistakes out over the plate, this guy is really a difference maker and a really good Major League player for us.”