How Adding a Sinker Transformed Mason Montgomery’s 2026 Season
Montgomery is yet another pitching development success story for the Pirates. His rise deserves more attention.
During the first half of the 2026 MLB season, the Pittsburgh Pirates were defined by one thing: a lack of bullpen depth, and more specifically, a lack of a lockdown closer.
Now, as the season enters its final stretch, the Pirates have reversed course, and their bullpen has been nothing short of stellar. As of the end of their series against the Los Angeles Angels, the club’s bullpen possesses the eighth-best bullpen ERA in the second half, turning one of their greater weaknesses into a true strength.
One of the main reasons for the sudden success of this group is the rise of Mason Montgomery, a flamethrowing left-hander who was among the three players acquired by the Pirates in the Brandon Lowe trade.
After struggling to command his pitches and find a way to tie his arsenal together, Montgomery has added a new pitch to his repertoire, begun pounding the strike zone, and certified himself as one of the best and most slept-on relievers in the sport.
The story of Montgomery’s breakout has been a deeply underappreciated story of the Pirates’ 2026 season, especially when hearing how it came to be. There was no question about whether or not he had the stuff to be a very successful big league arm; it was just a matter of putting things together, which is exactly what he’s done since the All-Star break.
Montgomery is yet another pitching development success story for the Pirates, and his rise should be given more praise than it has to this point.
The Addition of a Sinker
To fully grasp Montgomery’s second-half surge, you have to rewind the clock back to mid-June, when the Pirates packed their bags for a series at Coors Field.
Prior to this series, Montgomery’s season had been a mixed bag. To that point, he had pitched to a 4.18 ERA over 28 innings, notching 36 strikeouts. While he had been picking up punchouts left and right, Montgomery was allowing far too many free passes (15 walks in this period), and when he was hit, he was getting hit decently hard (8.5% barrel rate).
Seeing this, Pirates pitching coach Bill Murphy and the rest of their staff knew it was time for a change: Montgomery needed to add a sinker.
“It was in Colorado, and Bill just kind of presented the idea,” Montgomery said when asked about adding the pitch. “We talked about it with him and some of the other coaches, and yeah, I was open to trying it. Kind of got comfortable with it for about a week or so in catch play, and then brought it in.”
For most pitchers, going to Colorado does not tend to yield successful results. Pitchers don’t like to find themselves there because of the severe run environment in Coors Field and the high elevation that comes with it. These factors usually make pitchers’ stuff play worse than it really is, and lead to mixed results at best.
In Montgomery’s case, though, this was the beginning of a new chapter for his 2026 season.
After playing around with it in catch play for a little while and getting a feel for it, Montgomery first mixed the sinker into his arsenal in-game on June 23, and the results were quite encouraging. Out of the five times he threw it in this outing, it netted four swings, and of those, one whiff.
When it comes to adding a new pitch mid-season, there are certainly challenges along the way, as it won’t immediately become stellar overnight.
“Yeah, I think it can be,” Montgomery said regarding whether it was challenging to add a pitch mid-season.
“One is just getting comfortable with whatever grip it is and whatever pitch it is. Fortunately, the sinker was pretty easy to get comfortable with as far as, you know, throwing it where I want it to go. I think the other part of that is just having some trust in the pitch, knowing it’s going to work even if you do give up some hits or some damage. Just continuing to throw it more and more, and not being afraid to use it.”
Montgomery’s persistence in continuing to use it has paid dividends for him, as he’s been fantastic since the pitch first made its debut in-game. Following that outing, Montgomery has pitched to an astounding 1.16 ERA with 55 strikeouts in 31 innings pitched. Not only that, but he’s cut back on free passes tremendously, only walking eight batters in this period.
More interestingly, Montgomery’s four earned runs during this period have been split between just two games on June 26 and July 26. If you remove those two outings, he hasn’t surrendered a run in any of his other 30 appearances.
As for the sinker itself, it’s been incredible since being mixed into his arsenal full-time. As it currently stands, opponents are hitting just .125 against it, with a .190 wOBA and a whiff rate over 36% against the pitch.
“I would say I found it right away. I don’t think there was, like, you know, a lot of hesitation in the use of it of it to left or right. I think we have just been using it both [ways],” Montgomery said, regarding mixing the pitch into his plans of attack against both sides of the plate.
Even though he didn’t throw it for the first time until late June, it’s already become his second-most-used pitch in 2026, fully transforming his game on the hill.
Newfound Success in the Second Half
While Montgomery has been utterly dominant since fully adding his sinker to his arsenal, this stretch becomes even better if you look at his performance in the second half alone. Ever since the All-Star break, Montgomery has been one of the best relievers in the entire sport, beating out some tough competition in the process.
Montgomery has pitched to a 0.79 ERA across 22.2 innings in the second half, picking up 37 strikeouts in this period as well. He’s only walked six batters, and of the 85 batters he’s faced since the break, only nine have hit their way on base. Also, of the batters who’ve been lucky enough to reach base, 95.9% of them have been stranded.
Comparing this to other relievers around the league in this same span, Montgomery really begins to stand out. Only nine relievers have posted an ERA under 0.80 during this period, and of these arms, Montgomery possesses the highest strikeout rate (44.4%) by a wide margin.
To put Montgomery’s excellence in even more perspective, his ERA during this period is almost a full point better than Mason Miller’s ERA of 1.74. While Miller has him beat in strikeouts, Montgomery is able to go toe-to-toe with the superstar closer in many categories.
Zooming back out again, Montgomery’s underlying numbers have all been incredible as well. He’s posted a 37.9% whiff rate in 2026, a number that places him in the sport’s 99th percentile. On top of that, opponents have posted a barrel rate of 7.1%, in addition to an average exit velocity of just 87.9 mph.
That lethal mix of elite bat-missing ability and muted contact quality proves this post-break surge is no stroke of midseason luck. By pairing a sinker that neutralizes hard contact with secondary stuff that leaves hitters flailing, Montgomery has stripped opposing offenses of any viable blueprint against him.
Embracing the Closer Role and Finishing Strong
When the Pirates acquired Luke Weaver from the Mets in one of the biggest bullpen swaps of the 2026 MLB trade deadline, many expected that he would abandon the setup role he was in with the Mets and become the closer for his new squad. However, Montgomery’s rise has allowed Weaver to remain in an eighth-inning role, as he’s become the next closer in Pittsburgh.
Part of that role has been pitching on back-to-back days and closing games with regular frequency.
“Pretty well,” Pirates manager Don Kelly said Saturday when asked about how Montgomery has responded to more frequent usage. “I think that it’s something that we’ve talked about as we’ve gone through the season, too, of trying to take care of him… he’s doing a great job.”
Another part of becoming the closer and embracing that role is the birth of a new closer entrance, which Montgomery received for the first time on Friday against the Angels.
“It was pretty cool, man,” Montgomery said when asked about the closer entrance. “Yeah, it’s cool, you know, hearing the music, seeing the lights go down. It’s a fun time.”
Although he’s already had a great season, Montgomery’s goals to close out 2026 are simple: stay level-headed.
“Just stay consistent, man. Just stay consistent, level-headed, you know, not get too high, not get too low,” Montgomery said.
With baseball being a sport built on failure, taking every day one step at a time will be incredibly important for Montgomery. One thing is for certain, though: He’s emerged as a true star closer in Pittsburgh and a key piece of this bullpen for the foreseeable future.
All stats and rankings as of games on September 7.
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Written by
Jay Staph, a huge baseball fan and stat nerd, founded and ran his own baseball writing website, BSBWrites, at just 16-years-old. With focal points around prospects,…