Justin Martinez Talks About Adding the Sinker to his Arsenal

In addition to the splitter, the sinker may be a key to success for the hard throwing Diamondbacks reliever

Arizona Diamondbacks pitcher Justin Martinez (63) throws against the San Diego Padres / Michael Chow/The Republic / USA TODAY

Justin Martinez' breakout season has continued since we last wrote about him on May 11th. In that article we focused on how his splitter has become an elite pitch with tremendous movement, inducing very high swing and miss rates.

Since then he threw two more scoreless outings. In his last eight games he has thrown 9.2 innings, allowing just one run on seven hits with four unintentional walks and 14 strikeouts. For the season he has a 0.71 ERA to go with a 2.73 FIP and 16 strikeouts in 12.2 innings.

Besides the splitter, another pitch that has become an important weapon for him is the sinker. I was reminded on the X platform how he has introduced that pitch into his arsenal starting just this year.

Great stuff Jack! Glad one of my favorite pitchers is starting to get some love. For me, his sinker is also a huge development. He has never thrown a sinker until this season and it is truly elite. Opens up the rest of his arsenal especially to lefties

— DbacksMT (@JeffIrving16) May 12, 2024

It is indeed a completely new pitch for him, as he didn't throw it at all last year. He's currently used the sinker about 28% of the time. He's also is throwing his slider 26%, Splitter 24%, and Four Seam Fastball 21%.

The sinker is averaging 100.4 MPH, roughly the same as his four seamer at 99.9 MPH. There is no question about Martinez' ability to throw hard. And the movement on the splitter and slider are devastating when combined with his fastballs. If he throws strikes.

On Friday I had a chance to catch up with Martinez, and speaking through interpreter Alex Arpiza, he explained how and why the sinker development came about. Here is a brief transcription of that discussion.

How and why did you start throwing the Sinker? Was it your idea or coach's idea?

JM: "It was my idea. I noticed that when I would throw my fastball I wasn't really drawing any soft contact. I wasn't getting any double play balls. So I decided to implement the sinker. "

"I was playing with different grips and it came together in winter ball. Fernando Rodney helped me out and he showed me different grips with it."

So this is strictly achieved through grip change? You use the same arm slot, same tunnel?

JM: "Yes, it's the same motion. The grip is the only difference."

When you came back from winter ball did you work with any of the pitching coaches to discuss what you were trying out?

"Yes, I primarily worked with Fet [Bullpen coach Mike Fetters] and Strommie [Pitching coach Brent Strom] as well."

You've used a pretty even mix of all four pitches and it seems like you have a good feel for all of them. Is one feeling any stronger than the other at the moment?

JM: "If you guys notice, I'm not really throwing as many four seamers any more. I'm throwing more sinkers and I'm trying to evenly distribute the pitches so that the hitters are not just sitting on my four seam fastball. "

Torey talked about bringing you along step by step so that when it's your time, you're fully ready. How close do you feel you are from it being your time for high leverage situations?

JM: "Honestly I'm just trying to do my job. Trying to attack the strike zone, trying to avoid the walks. As for what Torey mentioned, I'm not sure how far I am or how close I am, I just know that when my time comes I'm going to be ready. "

You seem to handle the ups and downs of relieving really well and don't show it on your face when things aren't going well. How did you develop that demeanor?

JM: "It goes back to when I was a child, the upbringing that my parents instilled in me. They taught me to never think you're above anybody, to have humility. It extends from that."

Conclusion

Looking in on his Baseball Savant Page we can see he's given up a few hits on the pitch, but no extra base hits or anything hit too hard. The expected, or "x" stats on the sinker are very good.

The stuff+ rating on the sinker is 127, which ranks 10th best in MLB at the moment. That's pretty astonishing for a pitch he's never thrown before. His ground ball rate is up from 47% to 54%.

All of the above are extremely encouraging. But we are still in the realm of small sample size. As Martinez strives to improve and create a fuller arsenal, it will be interesting to track these developments.

Most importantly he'll need to continue to throw strikes and avoid walks. If he manages to do that, with his current arsenal the sky is the limit for the young fireballing reliever.