FanPost Friday: Matt Boyd, Mariners Secret Weapon

Rick Osentoski-USA TODAY Sports

Hello and welcome back to FanPost Friday! Poster flygutifly wrote this FanPost 18 days ago, but I still wanted to highlight it because hey guess what? He was right! Matt Boyd has now joined the bullpen/los Bomberos and has done quite well for himself so far in 2 innings pitched, allowing zero hits. Hooray for another hometown kid getting to live the dream! Anyways, give this quick post a read and laud flygutifly (whom I got to meet in person at softbaLL a couple weeks ago!) for being correct in his analysis. Have a great weekend, folks! Also, don't forget to join us at Growler Guys in North Seattle next Friday to watch the game with a bunch of fellow Mariners nerds!

With all the action at the trade deadline, it is easy to forget the Mariners added another arm to the pile in Matt Boyd. I think this move was particularly shrewd by Dipoto and co, because there’s a good chance it fits the Mariners needs in both the short and long term. The Mariners have shown enough prowess at finding and developing pitchers that when they make an under the radar move like this, it seems worth digging into what they might be seeing. So, I did just that (while taking a break from my usual Kelenic beat) and I am intrigued by what I found.

The added benefit Matt Boyd brings this year, and why I am calling him a "secret weapon," is a fresh left arm coming off the IL that I expect will look different from any of his previous performances. As other pitchers tire or hit innings restrictions, he should be fairly stretched out and hopefully fresh going into the home straight of the season. He will fill a swingman role to avoid overtaxing his arm coming off his long layoff: early reporting from the team suggests they are building him up to around 60 pitches, which should be good for outings of 2-3 innings.

To start with the basics, in 2021 Matt Boyd threw five pitches: four seam (42%), changeup (22.5%), slider (22.4%), curveball (7.6%), and sinker (5.5%). All his pitches move quite well, but in terms of results, the changeup and curveball have been his most effective. The sinker was thrown almost exclusively to lefties (90%) and in that limited capacity, it too has been effective. Here is a table of results for the pitches that had a WOBA under 300 last year.

















If I were to guess, I doubt there will be much change to these pitches aside from two-seamer usage maybe ticking up a bit. The Mariners pitching development team seems to be working on playing two- and four-seamers off each other, which we have seen be effective with both Robbie Ray and George Kirby. I also wouldn’t be surprised to see changeup utilization drop in favor of the curve, but I think those changes will be minimal.

Now for the fastball and the slider:













Where Boyd might have been lucky in terms of results on the changeup, he has been somewhat unlucky with his slider. I think that both the fastball and the slider could benefit from some tweaks. I will start with the fastball because that’s the easy one and the one that will see the most immediate improvement. Here is his heat map on the fastball from 2021:

From the heat map, it looks like he has fairly good command of the pitch. He has been deploying it in a more traditional usage pattern: trying to paint the edges with it and staying out of the middle of the zone. The highest utilization is the middle third of the zone on the outside edges. Interestingly, Matt Boyd’s release point is almost exactly the same as the Luis Castillo’s (but from the opposite side of the rubber). The relatively low arm action is producing a fastball with a VAA of -5.0. This isn’t elite, but it is a flatter than average and it should play up significantly if thrown in the upper third of the zone. (VAA explainer: here)

This should help the fastball produce more whiffs and weak contact. The Mariners have coveted and stockpiled pitchers with flat fastballs and Matt Boyd is the latest example. For reference, here is what Paul Sewald’s fastball heat map looks like this year:

With how flat Sewald’s fastball is, he can pump it in to the upper third of the zone with impunity. I expect Boyd’s heat map to shift upward in a similar utilization pattern.

The slider on the other hand, is more of a toss-up. It is an interesting pitch on its own and maybe the Mariners rely on the gap between WOBA and XWOBA closing without any overhaul. I personally doubt that and I have a strong suspicion they are going to rework the pitch. His slider would likely benefit greatly from being thrown harder, even if that means its movement decreases. He gets a good amount of sweep simply from the arm slot he throws from, so he could stand to lose some applied movement if he could trade that for velocity. By closing the velocity gap between his fastball and slider, it would make it more difficult for hitters to identify which pitch is coming their way. There is precedent for the team doing exactly this with both Muñoz and Brash. I suspect his slider at 84-85 mph with his arm slot will be a very interesting/effective pitch. A bullpen role is a great way to test out throwing that pitch harder to see how it works.

As part of this, I think the Mariners are working on a new type of reliever profile. I believe we are about to see reliever utilization change a little bit across the league. Due to roster limitations in place now, I think teams are going to increase value placed on relievers they think can go two or more innings. The Mariners are getting ahead of this wave a little bit. Matt Brash is a great example of this slightly longer outing reliever with great stuff that I think we will see more and more of. If there isn’t a spot in the rotation for Matt Boyd next year, I could see him evolve into a sort of 2-3 inning lefty swingman that the pen doesn’t have a good version of yet, especially if shorter outings result in his stuff ticking up. However, if the adjustments I suggested above and his health permit, I wouldn’t be surprised to see him be a solid 4/5 in our rotation next year. From a pure stuff perspective, I think he is a much more interesting option than Marco or Flexen.

I am so excited to see what version of Matt Boyd comes out of the Mariners pitching development lab. I will be keeping an eye on his statcast data when he rehabs to see if there are changes in how the breaking pitches are moving or their velocity. Hopefully, playing for his hometown team gives us a leg up on signing him to a 2- or 3-year extension. I have seen people discussing upgrading the 5th rotation spot or adding a lefty arm to the bullpen: I think that answer is already in house.