Photo provided by Eddie Provident
Isaac Mattson had a breakout season for the Pirates in 2025, and he did so while relying primarily on one pitch.
Mattson received his first extended look in the big leagues in his age-29 season a year ago and became a key piece in the Pirates bullpen. He finished the year 3-3 with a 2.45 ERA in 44 appearances, and he did so by throwing his four-seam fastball nearly 80% of the time.
Mattson started the 2026 season again in Pittsburgh’s bullpen, but the Pirates optioned the right-hander to Triple-A Indianapolis on May 20 so he could round out his arsenal and give opponents more to think about than just one of his offerings.
“Not necessarily a big change, but taking the things I worked on in the offseason and implementing those at a more consistent level,” Mattson said on what he worked on in the minor leagues. “Just felt like the attack plans versus hitters was very one-sided.”
It wasn’t easy for Mattson, just like it’s not easy for any player to get sent down. But he remembered the same thing happening to one of his teammates last year in a move that paid dividends.
Amidst a poor start to the season last year, the Pirates optioned David Bednar to Triple-A Indianapolis. After rejoining the team, the right-hander thrived and reclaimed his closer role until he was traded to the Yankees at the deadline.
“Seeing (Bednar) go through what he went through last year and how he was a professional through and through in the midst of something that everybody knew he didn’t want to be there, but he understood what it was going to take to get back to the big leagues,” Mattson reflected. “To his credit, he took those steps. Being able to see that last year really fed into my mindset in trying to be the best version of myself.”
In part due to what he did while he was with Indianapolis — a 1.86 ERA in nine appearances — and partly because of a desperate need in the big-league bullpen, the Pirates recalled Mattson over the weekend.
Mattson found success with his “invisible” fastball last year, but hitters were starting to see the pitch more clearly the more he threw it. He allowed seven runs on seven hits in 3.2 innings over his last five appearances before the Pirates chose to send him down to Triple-A.
Wanting to more effectively deploy all his weapons, Mattson compared his focus with Indianapolis to another sport.
“The approach was attack with my best weapon. I liken it to a golf outing. You can use your driver on every shot if you want, but there’s situations where a 9-iron or a putter is going to work better in that spot, depending on who you’re facing,” he explained. “That was the adjustment: How do I spread the deck and use everything that I have at my disposal – the slider, the changeup – to be able to level things out and compete at a higher level.”
Mattson, who was recalled on Saturday, was tested for the first time in Sunday’s loss to the Marlins. He entered the game in the eighth inning in relief of Brandan Bidois, who had allowed two runs on four hits and left with the bases loaded and two outs.
Mattson struck out Jakob Marsee to prevent any of his inherited runners to score. He went back out for the top of the ninth and worked around a pair of walks to deliver a scoreless frame.
In all, Mattson threw 27 pitches with more noticeable distribution — 12 were fastballs, seven were sliders, six were changeups and two were curveballs.
“I thought he threw the ball well,” manager Don Kelly said after the game. “He had the two walks in the last inning but he was able to navigate that. And really encouraging to see the velo up and the way he was able to use the off speed.”
For Mattson, he’s hoping his scoreless appearance his first time back with the Pirates is the first of many.
“I think the game teaches you lessons. When they’re the same lessons for a couple times in a row, that’s when you’ve got to make the adjustment. I’m excited to see what continues to happen.”
Mentioned in this article: Isaac Mattson Pittsburgh Pirates
More about:Pirates