Yankees’ multi-inning bullpen arm flashing improved fastball

Through his first four outings, Luke Weaver’s four-seamer sat at a modest 93.8 MPH, sporting a 4.70 ERA and generating a mere 5.7% strikeout rate. Since that stretch, the right-hander boasts a fastball sitting at 95.2 MPH, with a 3.38 ERA and 35.7% strikeout to pair with the velocity spike. The improvement of Weaver’s fastball has gone under the radar, as initially, the results didn’t line up with his improving stuff, as he wasn’t pitching well at first with the new velocity.

When the Yankees brought in Weaver last September, they felt as if there was something they could improve in his profile, and they’ve done exactly that thus far. His Stuff+ on the season (115) is his best grade since the metric began being tracked in the 2020 season. Last year, it sat at a below-average 95, and suddenly we’re seeing some serious tweaks to a fastball that most would have considered mediocre just a few months ago.

Immediately, the 35-point increase in Stuff+ stands out here, as the pitch quality has gone from well below the average for a four-seamer to well above. For context, last season Gerrit Cole had a 125 Stuff+ on his four-seam fastball, meaning that Weaver’s compares to the likes of the reigning Cy Young winner in terms of velocity and movement. A huge reason for that is the increase in vertical movement while also having a flatter angle to the plate.

Hitters are swinging underneath his four-seamer more often, and it’s helping his secondaries like the changeup perform a lot better since there’s a big gap in vertical movement from his fastball, and hitters are chasing and whiffing frequently at it. Simplified mechanics with more focus on getting behind this pitch have resulted in it getting more backspin and carry in its ball flight, and the results are better across the board as a result.

Despite the lack of attention that he’s received, Luke Weaver is easily the most-improved pitcher from last season on a pure stuff basis, and as a potential multi-inning weapon he could help this pitching staff. Innings could be hard to come by, and we saw in a win like last night’s how crucial having a long relief arm can be to save your bullpen. The Yankees only had to use Ian Hamilton for one inning in this game, likely keeping him fresh for the final game of the series today.

This is one of the most unusual bullpens we’ve seen in a while for the Yankees, as we had continuity from 2021-2023 in regards to what the pecking order was. Clay Holmes, Jonathan Loaisiga, Michael King, and Wandy Peralta were staples in those bullpens, and yet the Yankees are without all but one as of right now. The UCL injury suffered by Loaisiga put a strain on this bullpen, and the hip injury to Nick Burdi would only hurt that depth more.

Right now, the Yankees are heavily reliant on pitchers who are hoping to improve off of their 2023 campaigns, and they signed Luke Weaver to do exactly that. He was in contention for the fifth starter job when Gerrit Cole went down with his elbow injury, but he can still provide incredible value if he’s able to build upon this recent string of strong outings. The velocity is genuinely very intriguing, and if we see a 94-95 MPH version of Weaver compounded with the movement and location up in the zone, he might just be a reliable multi-inning option.

What Michael King provided to the bullpen was invaluable, and it served as a great way to bridge the game to Clay Holmes in the ninth inning. They’ve tried Jonathan Loaisiga and Ian Hamilton out in those roles, but perhaps it’s Luke Weaver who gets that job done. When the team moved King to the rotation, it seemed as if the Yankees were grooming Jhony Brito for that role, and perhaps that’s what they’re doing with Weaver here.

I’m all-in on the Luke Weaver train with the progressions he’s made with the fastball, and hopefully, he can stay healthy enough to see the stuff gains translate to full-season results.