Robert Stephenson – 44.4% Slider Whiff Rate
Calculating whiff is pretty simple. It’s the number of swings and misses divided by the number of total swings taken. Robert Stephenson stands out with a 44.4% whiff rate on his slider, making it a truly deadly weapon. Stephenson made some major adjustments to his pitching repertoire with the Pittsburgh Pirates, and it worked out well for him after the acquisition.
It was only 13 total innings, but Stephenson held batters to a .170 batting average and .264 wOBA with his slider. There were only 13 pitchers in 2022 that faced 100+ batters and had a whiff rate of 44% or higher, and Stephenson was one of them. With a 44.4% whiff rate, you’re talking about a pitch that gets more swings and misses than Gerrit Cole’s slider or Dylan Cease’s slider.
So how can the Pirates take advantage of this? Well, it looks like they already have. Stephenson’s slider usage rate was just 45% during his time with the Colorado Rockies. However, after the Pirates claimed Stephenson off waivers, he used his slider nearly 70% of the time (69.4%, to be exact). He used his fastball a whole lot less as well, going from 53.6% to just 28.2%. There’s a good reason, as while his slider was nasty, his fastball was demolished to a .459 wOBA.
That big change in pitch arsenal will significantly work in Stephenson’s favor next season. Batters can’t hit his slider, and using it about three-quarters of the time seems like a no-brainer move. Sure, his fastball still isn’t great, but he also started to re-incorporate his curveball into the mix, which could even further lessen his four-seamer usage.