Pittsburgh Pirates: How Robert Stephenson Can Figure It Out

Over the weekend the Pittsburgh Pirates claimed reliever Robert Stephenson. Can they ‘fix’ him and turn him into a quality bullpen arm?

The Pittsburgh Pirates recently claimed righty reliever Robert Stephenson from the Colorado Rockies. There’s no way to sugarcoat his 2022 campaign. He’s been awful, posting a 6.04 ERA, 4.67 FIP, and 1.04 WHIP. Home runs have been a massive issue for Stephenson with a 1.60 HR/9, but he’s seen his strikeout rate go from 30% in 2019 to just 18.8% in 2022. However, there are ways the Pirates can figure out the talented reliever and make him a quality arm once again.

There are two types of spin when you throw a baseball. There’s active spin, which is the spin that contributes to movement, and then there’s gyro spin, which is spin that doesn’t contribute to movement. You want your fastball to have a high active spin percentage but a high gyro spin percentage on your slider. These are two things Stephenson has a lot of on his four-seamer and slider.

Stephenson is in the top 92nd percentile of fastball velocity and in the top 85th percentile of spin rate. Stephenson’s active spin rate on his fastball is 99.3%, the 25th highest active spin rate in baseball. His slider averages out over 2900 RPM with an active spin rate of 38.2%. His slider has over 40 inches of drop.

It’s no coincidence Stephenson’s best season was arguably 2019, when he used his slider more often than his fastball. During that year, he had a 3.76 ERA, 3.63 FIP, and 1.04 WHIP. His 30% K-rate is still a career-best, and he also kept batters to an average below the Mendoza line at .181. Stephenson struck out a ton of batters but also kept them off balance. He limited opposing hitters to an 87.3 MPH exit velocity (top 80th percentile) and 26.8% hard-hit rate (top 98th percentile).

Stephenson used his slider 55.6% of the time in 2019, and opponents couldn’t touch the pitch. They managed just a .125 batting average and .185 wOBA against his slider. It’s still a highly effective pitch this year. He’s managed just a .179 average against it with a .290 wOBA. His slider has a higher whiff rate than either Shohei Ohtani or Gerrit Cole have with their sliders, and his strikeout rate of 34.9% is higher than Cole and Clayton Kershaw. His -17 run value on his slider in 2019 was the 8th best in the league.

Stephenson’s slider needs to become his primary pitch again. But he also needs to adopt a new pitch over his four-seamer. His four-seamer has consistently been a below-average offering, even with the high velocity, spin rate, and active spin rate. Every year, his run value on his four-seamer has been in the positives. Last year when he had a 3.13 ERA and career-best home run rate and K:BB ratio, his four-seamer still had a run value of +3. Right now, his fastball has a run value of +7.

The Pittsburgh Pirates have found success teaching some of their pitchers a two-seamer/sinker. I think this is a strategy that the Pirates and Stephenson should try. Stephenson also threw a curveball last year with great results. He tossed it 20.9% of the time, holding batters to a .143 average, .197 wOBA, and 84.3 MPH exit velocity against it. It had a -4 run value and -2.2 RV/100.

His slider is an elite pitch already. He needs a second pitch, and his four-seamer isn’t cutting it. The first thing the Pirates need to do is make him throw his slider a lot more often, at least 50% of the time but preferably more often. After that, they need to add a secondary pitch to his arsenal, which could be a two-seamer or another breaking ball.

Finally, they need him to almost completley drop his four-seamer. A slider/two-seamer or slider/curveball pitcher isn’t typical, but if that’s what needs to be done to make Stephenson effective, the Pittsburgh Pirates should do it.