Mariners reliever Edwin Diaz credits teammate for nearly unhittable slider

HOUSTON — Mariners rookie reliever Edwin Diaz is on some kind of tear. He currently holds an MLB-best ratio of 17.02 strikeout per nine innings pitched (among all relievers with 14 or more outings). His 10 consecutive outs via the strikeout has tied the club record set by Randy Johnson in 1997. As good as he was in his first outing, where he flashed the 101 mph fastball, he has since improved by going from dominant with the velocity to flat-out nasty each time out. difference according to manager Scott Servais?

So what’s the difference?

“The development of his slider,” manager Scott Servais said before the Mariners July 4 matchup with the Astros. “Everyone knows he throws hard — we knew that, we knew we were getting that — but the development of his secondary pitch has been huge.”

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Huge indeed, and it didn’t just happen automatically. Diaz had a slider when he first arrived in the big leagues, but two weeks ago he made a change with his grip, testing out the pitch during bullpen sessions and while playing catch. He first introduced the pitch in a game against the Pirates last week, throwing three of them in his 17-pitch outing. Why the change?

“The other one doesn’t break a lot,” Diaz said Monday morning. “They show me a new grip, I start practicing, playing catch and then I throw in the game and now everybody talks about my slider.”

Everyone including his skipper.

“There is a marked difference since when he got here to now,” Servais said. “They’re missing it. It’s hard, it’s late. When you throw that hard, at 97 to 98, you have to cheat for the breaking ball, and when the breaking ball is coming out of the same window with the late depth at 87, 88, it’s really, really good.”

Diaz said an assist from a teammate in the bullpen and a coach have made the difference.

“(Joaquin) Benoit and the pitching coach (Mel Stottlemyre Jr.), they talk to me about the grip,” Diaz said.

Turns out that while the 38-year-old Benoit has had his struggles this season and hasn’t always been able to do what he wants to do to help the team on the hill, he’s had an eye out for Diaz. Behind the scenes, the work he has done with the rookie could benefit the Mariners for a long, long time. Benoit, a 15-year veteran, is not one to look over his shoulder at the oncoming competition for his position. Rather, he sits side-by-side with Diaz at their lockers on the road and in the bullpen — always talking and always teaching.

“Everybody talks to me, but basically Benoit talks to me a lot,” Diaz said. “He talks to me a lot about the game, how to setup the batter, how to get outs. How to read swings.”

And how to throw a pitch that has absolutely stymied opposing hitters. Since that first game when Diaz tried the new slider grip, he has thrown the pitch 15 times, generating 11 strikes, 10 of which were swings and misses. He has thrown it a total of 18 times and only once has it resulted in a hit by the opposing batter.

“Going through a team like he did with Baltimore, that’s a really good lineup,” Servais points out. “At times Diaz overpowered that lineup. The velocity on the ball and the lateness to the break, that’s what separates the average breaking pitch to the above average.”

The pitch has helped Diaz smooth the transition not only to the big leagues but also the bullpen. A lifelong starter, Diaz is now very comfortable working in relief.

“I like everything,” he answered when asked what he enjoys about being a reliever. “I like having fun in the bullpen. I feel more in the game, more mentally prepared for situations. I love being in the bullpen.”

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