Drew Rasmussen Made Sweeping Changes to His Slider

Drew Rasmussen was a Rays success story last year. A key part of the trade that sent Willy Adames to Milwaukee, Rasmussen profiled as a plus reliever. But after initially serving as a multi-inning bullpen arm, Tampa Bay slotted him into the rotation for the last two months of the season, and he delivered 37 innings of 1.46 ERA, 2.76 FIP excellence. Sure, it was over 4.5 innings per start, and the peripherals weren’t pretty, but quality over quantity has always been a deal the Rays will take, and you certainly can’t argue with his run prevention.
Rasmussen did it despite what could charitably be described as a predictable arsenal. He threw his fastball 65% of the time and his slider another 30% of the time. If we’re being honest, it was more like 1.5 pitches — his fastball did a lot of the heavy lifting, and the slider picked up the pieces. It’s one of those spin-and-speed four-seamers that are all the rage these days. Rasmussen didn’t always locate it well, but simply put, it’s a hard pitch to hit.
He paired that fastball with a slider that featured two-plane action. It wasn’t a big movement pitch; it had drop and arm-side run in roughly equal proportion, but its main standout quality was that it was an offspeed pitch when hitters were setting up for 98 mph at the letters. If you’re trying to cover a high fastball, particularly one that struck you out last at-bat like this:
Then it’s hard to adjust to a slow and low pitch like this:
When you look at it that way, it’s a pretty good pitch. And hey, by some metrics, it was: hitters had a lot of trouble squaring it up, mustering a woeful .226 wOBA on contact (and a 41% hard-hit rate). On the other hand, it hardly missed any bats; Rasmussen was in the bottom 10% of baseball for swinging strike rate and bottom 15% for CSW rate. Eno Sarris wrote about the pitch in the playoffs and came away similarly unsure of its efficacy. Read the rest of this entry »