The Pittsburgh Pirates relief pitcher Isaac Mattson detailed his off-season focus.
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.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.”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. Sep 7, 2025; Pittsburgh, Pennsylvania, USA; Pittsburgh Pirates relief pitcher Isaac Mattson pitches against the Milwaukee Brewers during the eighth inning at PNC Park. Mandatory Credit: Charles LeClaire-Imagn Images | Charles LeClaire-Imagn Images“I think every year you walk into it with the expectation of winning and winning at a high level. And I feel like that's where this group's at,” Mattson said. “Still have to put in the work… I feel like as a group we're excited for 2026.” Central to that culture, according to Mattson, is the influence of manager Don Kelly, whose own journey as a gritty, 11-year major league veteran resonates deeply with a roster filled with determined players. “We all kind of know backstory and how he worked his tail off to play in the big leagues as long as he did,” Mattson said. “Being able to look at a guy like that and also know a guy like that leading this group, it just amplifies all of our background.”“There's an expectation that's always set… but also knowing there's experiences that we all bring to the table, knowing that there's an understanding that there's gonna be days where we struggle. Knowing there's a guy in our corner like is gonna be huge for all of us.” Mattson also addressed the trade of veteran reliever David Bednar, a move that altered the bullpen’s late-inning hierarchy. “I think it's gonna be a different look just like it was at the ,” he acknowledged. “But being able to step into that role with confidence from the experiences you had before and know that at the end of the day it's still our job to make outs, throw strikes. Doing our best to simplify it that way allows us to go out and play free.” The message was clear: the work is focused, the culture is strong and the expectations for 2026 are higher than ever.Ethan Merrill is from Grand Rapids, MI, and brings with him a diverse background of experiences. After graduating from Michigan State University with a degree in journalism, he worked with the Arizona Diamondbacks for three seasons before settling in the Pittsburgh area in 2020. With a passion for sports and a growing connection to his community, Ethan brings a fresh perspective to covering the Pittsburgh Pirates.
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