PITTSBURGH -- A young Buc celebrated an MLB first off Cardinals starter J.A. Happ, but once again, the Pirates’ offense was frigid against the veteran lefty.

Happ threw six innings with only one hit allowed against the Bucs in their 4-1 loss to the Cardinals on Tuesday at PNC Park.

• Box score

The Cardinals’ starter began the game in similar fashion to when he held the Pirates hitless through 7 1/3 innings on April 23 as a member of the Twins. This time, it was nine up, nine down with three strikeouts in Happ’s first time through the Bucs’ order.

But in the bottom of the fourth inning, second baseman Hoy Jun Park, who struck out on a pitch that appeared to be out of the strike zone in his first at-bat, came to the plate. The super-versatile player, whom the Pirates acquired from the Yankees for Clay Holmes at the Trade Deadline, sent a 1-1 fastball from Happ into the right-field seats for his first career home run.

“I’m just trying to be on time every time,” Park said. “I knew J.A. Happ is a really great pitcher, so I was trying to focus on every at-bat. I hit it on time at the plate; I just got a good pitch to hit.”

The ball traveled a Statcast-projected 379 feet, but the more important number for Park was a 30-degree launch angle. Why? Pirates starter Steven Brault, who allowed two runs in five innings on Tuesday, had been giving Park grief about hitting so many gap-to-gap balls instead of lifting them for dingers.

Brault said with a smile that Park approached him after the homer to ask if that was a good enough launch angle for him.

“It was cool to see, because J.A. Happ, he’s a seasoned veteran,” Brault said. “He’s been around for a long time. That’s a cool first home run for Hoy, so I’m super excited for him, and I think he’ll hit a good amount more.”

Putting the left-handed-hitting Park in the leadoff spot against a lefty would seem on paper to go against the matchup trend that Pittsburgh manager Derek Shelton has turned to for his lineup constructions throughout the year. But Park is making his case to change that: In his first three at-bats vs. left-handers in MLB, he has a double off Milwaukee’s Brent Suter and a home run off Happ.

“In Triple-A, I hit a pretty good number of left-handed pitchers,” Park said. “I believe in myself that it’s going to be good, that it’s going to help the team.”

“Today, we saw that as a good opportunity versus a left-hander,” Shelton said. “He had a good swing against him, so he’s going to continue to get opportunities.”

However, it ended up being the only hit of the night for the Pirates, who went 1-for-26 with eight strikeouts, with the bulk of that dominance coming from Happ. A former Buc, he admitted being back in his old stomping grounds may have motivated him a bit more on Tuesday.

“I don’t think it’s anything against this team per se,” Happ said. “But ... I think this might be my first time back pitching in this ballpark since I was here in ’15 -- and [I have] great memories from those couple of months. My son [J.J.] was born here, and just some fun memories kind of coming back and being downtown in the area here. And beautiful ballpark, of course.”

The level of production Happ has enjoyed against the Pirates is a bit perplexing giving his overall numbers this season. Against teams not named the Bucs, he has a 7.13 ERA; against Pittsburgh, that number is a miniscule 0.68.

“I think both times we’ve faced him, he’s executed balls on both sides of the plate,” Shelton said. “He’s given us trouble.”

“He was on, and we couldn’t capitalize, and that’s OK,” Brault said. “I think he’s a good pitcher, and he had a good night tonight. It’s hard to beat those guys when they’re on.”