Pirates Pitcher Eyes Next Step in Evolution

Surrounded by reporters and cameras during PiratesFest at the David L. Lawrence Convention Center last week, reliever Isaac Mattson exuded a quiet confidence. This confidence has seemingly carried over from his performance on the mound last season, when Mattson established himself as a high-leverage reliever in the Pittsburgh Pirates' bullpen.

Mattson, an Erie, PA native who attended the University of Pittsburgh, seems to have found a baseball home not far from where his journey began. Given Mattson's background, it was easy for him to garner the support of Pirates' fans.

His performance on the field only bolstered this transition to becoming a fan favorite. In 47.2 innings, Mattson pitched to a 2.45 ERA, with 45 strikeouts and 19 walks. Mattson debuted for the Baltimore Orioles in 2021, but only pitched a total of 9.2 innings in the majors before last season. He had a short stint in the Pirates' bullpen at the end of the 2024 season. The 30-year-old was still technically a rookie when he was called up to Pittsburgh on May 22nd of last year.

The Invisible Fastball

Mattson's most effective weapon was his four-seam fastball that dives down on opposing hitters. Last year, Mattson's fastball was in the 91st percentile of vertical movement for all MLB fastballs, with an average of 17.8 inches of induced break. He used the pitch 78.5% of the time, which was in the 99th percentile of all pitchers.

During scheduled media availability at PiratesFest, the right-handed pitcher talked about the unique characteristics of his "disappearing" fastball that emerged as his putaway pitch.

When jokingly asked if his catchers are provided an extra Pitchcom button for his unique four-seamer, Mattson demystified the pitch.

“Nah, usually it's just fastball up, fastball down, fastball away,” he said. “From there it's just execute to a spot.”

While acknowledging the strength of his fastball offering last season, Mattson also admitted that the "secret is out" about his fastball. Evolving his pitch mix will be key to evolving as an effective reliever.

Mattson’s focus this offseason has been on developing his secondary pitches, particularly a changeup he believes can elevate his game. He was wisely reluctant to reveal too much, but that focus was clear.

“Without giving too much away… Changeup being the biggest piece,” he shared. “I felt like, especially the second half of the season, learned some lessons to grow from. Worked on the changeup a lot this year. Gonna work on that continuing through spring training and just try to refine that to where it needs to be. I'm excited for where that can take me.”

Mattson credited new pitching coach Bill Murphy and his staff for their role in his off-season development, specifically with his new changeup. “There's a depth of knowledge that they bring to the table. They've been really, really big in the implementation of the new changeup for me. The communication has always been there.”

He also expressed enthusiasm for how the pitching staff, under the guidance of Murphy and his team, will be deployed.

“Yeah, I'm excited for how we're gonna get used… it'll be really fun to see just how filthy we can be this year,” he said.