Alex Rubinson - Austin Warren is Proof that David Stearns still has his Fastball

In January, 2025, the New York Mets made an acquisition that popped up on the transaction wire that most fans and media paid barely any attention to. David Stearns claimed a reliever, Austin Warren, off of waivers from the San Francisco Giants. The relief pitcher had made just eight total appearances over the previous two seasons with the Giants and Los Angeles Angels. January is typically a time when front offices are looking for arms to just get the team through spring training. Warren appeared to fit that mold. 

He stuck around for the entire season with the organization, but bounced between the big league club and the team’s Triple-A team in Syracuse. Although he impressed in limited playing time, he only tossed just over nine innings. During the offseason, the Mets spent big to replace Edwin Diaz at the back of their pen by signing Luke Weaver and Devin Williams along with acquiring Tobias Myers, and Warren failed to break camp with the team. 

Over the last month, Warren’s 2026 season has mirrored his 2025 campaign with being transported back and forth between Syracuse and Queens. While the Mets have struggled to open the season, the bullpen has been pretty steady. As the Mets continue to navigate the long grueling summer months, Warren has proven and earned the opportunity to stick with the team for the foreseeable future. 

Warren has not made more than 16 appearances once in a single season but entering Wednesday, he has already toed the rubber 10 times to start 2026. He has stuck out as one of New York’s top relievers who should continue to get high-leverage opportunities, as he has recorded a miniscule 0.69 ERA and a WHIP that is barely north of 1.00. Although it’s difficult to say that Warren will carry those numbers through a full season, he should give the Mets quality innings and can be used in a variety of situations. 

In an era when teams are constantly chasing velocity, Warren breaks that trend. His fastball averages just under 94 MPH. It’s funny to think about a 94 MPH pitch being unimpressive, but that’s the reality we live in in 2026. Due to him not overpowering opposing hitters, his strikeout and whiff numbers aren’t anything to brag home about, but that doesn’t mean he is not effective. His fastball is still an above average pitch in terms of run value with his breaking stuff generating a plus two when it comes to run value. 

His mediocre velocity plays a role in Warren using his sweeper as his primary pitch. The right-hander throws the sweeper almost half of the time. The sweeper will be the pitch to watch moving forward because hitters are hitting just a touch above .210 against it, but the expected average is over 50 points north of that. This isn’t to say it’s a bad pitch, but hitters might be guessing sweeper based on how often he throws it. Warren also has yet to give up a knock against his sinker. That rate will not continue, but it does show that hitters are unable to square up the pitch. 

Meanwhile, Warren’s fastball has been unlucky. Batters are hitting over .285 against the offering but are expected to hit under .165. The most eye-popping difference is slugging. As of now, hitters are mashing against the fastball to the tune of an .857 slugging percentage, but the expected slug is less than half of that at just .367. His four-seamer has a lower expected weighted on-base than both the sinker and sweeper, but the actual weighted on-base is north of .480. 

At first glance, one would expect the quality of the contact to be weak and the ball is just finding green grass, but batters do have an exit velocity of 97 MPH on the pitch. On the other hand, there is also a 50% whiff rate. At the end of the day, hitters aren’t making a ton of contact despite the less than stellar velocity, but due to the lack of velocity, hitters are squaring up the pitch when they do put the bat on the ball. 

Looking at guys that throw hard like Mason Miller or Jacob Misiorowski, they can afford to make a mistake or two. Due to their stuff being so nasty, they can get away with missing locations. With Warren, he has proven to be a very good pitcher with a 94 MPH fastball, but he doesn’t have nearly as much wiggle room if he misses his spot.

The biggest difference in Warren’s repertoire between his first season with New York and this year is how often he is mixing in his curveball. Granted, he didn’t pitch a lot last year, but he only threw his curveball once. This season, the reliever is tossing it almost 12% of the time. The curveball has produced the lowest exit velocity of any one of his pitches. 

Warren has also ditched his cutter (a pitch he threw 17% of time a season ago). Justin Willard and company should encourage Warren to throw the curveball at a higher rate. There might come a point where he is throwing the pitch too often, but we haven’t reached that threshold yet. Whenever a pitcher is discovering a new pitch or playing around with his repertoire, he shouldn’t be afraid to test the limits. He can always back off when he has crossed the line.  

The reliever has made strides even from last year. His hard hit rate is down 11% compared to 2025 with his expected weighted on base average down 35 points. Warren’s expected stats do show that his sub 1.00 ERA is probably not sustainable. Instead, he projects as a guy who will have an ERA in the mid 3.00s with an opponent batting average settling in about .215 (not ~ .155). Either way, Warren is a cheap option that can be trusted and relied upon to pitch in a variety of roles. 

Carlos Mendoza should continue to use him in high leverage scenarios until those sparkling actual numbers resemble more of the expected metrics. Stearns has been far from perfect during his Mets tenure, but he has always found hidden gems in the reliever market, and that part of his game still hasn’t wavered.