Justin Slaten is a pitching prospect from the Texas Rangers. A third-round pick in 2019, Slaten started his pro career as a starting pitcher; however, he posted an ERA over 6.00 and a WHIP above 1.50 in each of his first three pro seasons. But Slaten was moved to the bullpen full-time last season, and it paid dividends for him, at least performance-wise.
Slaten spent most of his season at the Rangers’ Double-A affiliate, where he pitched to a 3.16 ERA and 1.14 WHIP in 51.1 innings. The right-hander struck out 37.5% of the batters he faced with a walk rate of only 7.9%. Slaten, however, had a mediocre 1.58 HR/9. But in his defense, Slaten had an HR/FB ratio of 23.7%. It was the third-highest HR/FB ratio among all Double-A pitchers and the 8th-highest ratio any Double-A pitcher has had over the last five minor league seasons. I doubt he will carry this over to next season. Slaten had a 3.95 FIP, but once adjusting for this insanely high HR/FB ratio, the right-hander had an xFIP of just 2.82.
His strong numbers at Double-A earned him a late-season promotion to Triple-A, where he tossed 8.1 innings, only allowed one earned run, and struck out ten batters while walking four. It was a small sample size, so don’t take it too seriously, but it gives us some pitch-tracking data to examine.
Slaten has good velocity, sitting 95-97 MPH and topping out around 98. On top of that, he has above-average spin at 2300-2400 RPM. This pitch can ride through the zone, unlike many others. His slider comes in around 83-95 MPH but with over 2500 RPM of spin. FanGraphs describes this pitch as a knee-buckler. His cutter is also a regularly used part of his arsenal, and it comes in around 87-90 MPH with 2350-2450 RPM on average.
The right-hander can generate above-average velocity with a relatively low-effort delivery. Standing at 6’4”, 222 pounds, Slaten has a strong build. His arm slot is an over-head delivery, so we aren’t looking at someone with an overly deceptive motion on the mound.
FanGraphs is very bullish on Slaten, ranking him as the Texas Rangers’ 19th-best prospect. Sure, all prospect rankings are subjective, but ranking top 20 on a major outlet like FanGraphs is nothing to scoff at. But do keep in mind that neither Baseball America nor MLB Pipeline put Slaten even in their top 30. He may be a top 20 prospect by FanGraphs’ analysis, but he is not a consensus top 20 Rangers prospect. Still, Slaten would be one of the better relief prospects in the Rule 5 draft.