PITTSBURGH — The Washington Nationals want to raise the floor of their roster. They’ll do it in any way they can, be it via waiver claims, trades or future drafts. The fruits of their labor in those avenues, though, will take a while. So, in the mean time, the Nationals can improve their roster through the most obvious avenue: developing the talent they have.

Mitchell Parker, who starred in relief in the Nationals’ 5-4 win over the Pirates on Tuesday night, is the latest example of doing just that.

Thanks to a revamped pitch mix, Parker struck out five hitters over two innings. He finally allowed a pair of hits in the seventh and exited with the bases loaded and the Nationals (8-9) clinging to a one-run lead.

But Cionel Pérez induced an inning-ending double play in the next at-bat. He yelled in excitement in the direction of the Nationals dugout. Later, the Pirates (10-7) left the tying run stranded on second in the ninth.

Four Nationals relievers combined to pitch 4 2/3 scoreless innings to seal the win. And that stretch was kickstarted by Parker, who opened the season in Rochester but showed how much he’d grown in one offseason.

“Honestly, just confidence,” Parker said when asked what stood out about his outing. “I feel like that’s something that kind of came and went last year.”

“The staff in Rochester has done an outstanding job with Mitchell,” manager Blake Butera said. “Comes in a game, one-run lead right there on the road and is able to do what he’s doing. Not just the same Mitchell you saw last year, even better.”

At first glance, Parker didn’t look like a different pitcher as he stepped on the mound for his first big league appearance of the season. His unique over-the-top delivery remained. So did his stoic demeanor.

Then, the ball left his hand. The sequence of pitches that followed his first was proof that Parker was, in many ways, different.

Parker was one of the worst pitchers in baseball last season statistically. He had the second-highest ERA (5.68) and WHIP (1.43) among qualified starters a year ago. By the end of the season, he had been relegated to the bullpen.

In 2025, Parker threw his four-seam fastball 55.5% of the time. He threw his curveball primarily to right-handed hitters and his slider to left-handed hitters. There wasn’t much guess work for opposing hitters, especially if he lacked command.

The Nationals encouraged Parker this spring to lean into throwing his slider more. That’s not to say his fastball isn’t good. In fact, his fastball velocity was up a tick on Tuesday. But Parker’s slider is an asset.

“All of our guys, we try to lean into strengths and he has a really good slider,” Butera said.

By the end of his outing, sliders accounted for 29 of his 46 pitches. The remainder were 10 four-seam fastballs, six curveballs and a splitter. But his slider generated nine whiffs in 21 swings (43%).

“It’s a pitch that we’ve been throwing a lot during the spring,” Parker said. “It’s a pitch that we’re starting to really like and we can build the other three around it, we’ll be in the good spot.”

In the top of the first, the Nationals grabbed an early 3-0 lead. James Wood and Luis García Jr. walked. Wood stole third. Then, Brady House, Daylen Lile and CJ Abrams hit RBI singles in the ensuing at-bats.

The Nationals initially tabbed Miles Mikolas to start against the Pirates. But earlier this week, Ken Waldichuk was placed on the 15-day injured list and Butera said he’ll likely need Tommy John surgery.

That left the Nationals with two lefties (Pérez and PJ Poulin) against a Pirates lineup that features three lefty batters in its first four spots. So Poulin pitched the first inning, allowing a solo homer to Brandon Lowe.

Abrams hit a solo shot in the third, his sixth homer of the year, to push the Nationals ahead 4-1.

Mikolas relieved Poulin and pitched two scoreless frames before running into trouble in the fourth. Marcell Ozuna hit an RBI double and Nick Gonzales added an RBI groundout. Joey Bart added a solo homer in the fifth that ended Mikolas’ outing, setting up Parker to face the Pirates’ lefties at the top of the order.

“That was about what we had kind of planned to do,” Butera said. “With their left-handed hitters, wanted to try to get them some tough looks, at least as tough as we could lay it out.”

Parker struck out Oneil Cruz and Lowe with sliders. He threw that pitch with confidence in any circumstance — for early strikes and for late swings and misses. Against righties and lefties.

“Just looked nasty,” Abrams said. “It was good stuff, just doing his thing out there and it was cool to me.”

The Pirates likely had a different scouting report on Parker. The more he pitches, the more he’ll have to adjust. It’s possible he could be optioned back to Rochester in the near future. But on Tuesday, his game plan helped the Nationals even the series.

“Just something to keep building on,” Parker said. “It’s a good base and just got to keep building on that base.”