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Dan Warthen's slider has helped make superstars of Jacob deGrom, Matt Harvey, and Jeurys Familia

The Mets' pitching coach has been teaching his young pitchers how to throw a more effective slider.

Anthony Gruppuso-USA TODAY Sports

Dan Warthen has been the Mets' pitching coach since the middle of the 2008 season when he replaced Rick Peterson. Often overlooked, Warthen has worked with his fair share of power arms in his time with the Mets. In just the last few years alone, he’s been able to help groom superstar pitchers out of guys like Jacob deGrom, Matt Harvey, and Jeurys Familia. So, what’s his secret? Well, according to Warthen, it all starts with the power slider he’s taught to his young pitchers.

In a profile for Fangraphs, Eno Sarris analyzes Warthen's slider and has found that Mets pitchers throw the hardest sliders in MLB. The three fireballers in Harvey, Familia, and deGrom all fall in the top 15 in slider velocity. But raw velocity is not all that matters. What has been important for the Mets' pitchers is the relatively small difference in velocity between their sliders and their fastballs. The key to Warthen's slider is that it looks like a fastball but moves—late—like an off-speed pitch. Warthen himself explained how he’s changed the way he’s taught his young pitchers to throw the slider.

"It’s a different spin, it’s a different grip. The whole idea is not to use your wrist to try and spin the ball, you want your fingers to spin the ball. You’re thinking fastball and just kind of cutting through the ball"

Check out the rest of Sarris's profile—including research, analysis, and interviews—about Warthen's slider at Fangraphs.