Pittsburgh Pirates: How Jose Hernandez Can Build On His Rookie Year

Jose Hernandez had an up and down rookie campaign in 2023, but here's how the lefty reliever can build upon it next season

Typically, Rule 5 draft picks are a complete shot in the dark. That’s why so few ever become productive major leaguers. But once in a while, you’ll find a diamond in the rough. Last year, the Pittsburgh Pirates took left-handed reliever Jose Hernandez from the LA Dodgers, and while his season had a ton of positives, it also had a handful of negatives.

The best way to describe Hernandez’s rookie campaign was a tale of two seasons. Hernandez finished the first half of the year as one of the top rookie relievers. His first 27.1 innings saw him pitch to the tune of a 2.63 ERA, 3.40 FIP, and 1.02 WHIP. Hernandez owned both an above average 25.7% strikeout rate and 0.99 HR/9. But he only had a 5.5% walk rate, the 4th lowest among rookie relievers with 20+ innings pitched.

But Hernandez ended the first half on the injury list. He wouldn’t throw on a MLB mound from June 17th through July 24th. When he returned, the numbers weren’t nearly as pretty. His final 23.1 innings yielded a 7.71 ERA, 5.74 FIP, and 1.76 WHIP. Hernandez upped his strikeout rate to 29.8%, however his walk rate and home run rate both skyrocketed to 14% and 2.31-per-9, respectively.

Hernandez’s bread and butter pitches were his slider and four-seam fastball. He used his slider 55.9% of the time, and his fastball at a 33.2% rate. His changeup made up 10.9% of the pitches he threw, and he only used them against same-handed batters.

So what happened between the first half of the season to the second half? I don’t think it was the injury, but perhaps his change in approach. He became somewhat predictable, in my opinion. In the first half, he used his slider 49% of the time, his fastball 32.3% of the time, and his change-up at an 18.7% rate. But in the second half, he used his slider 62% of the time, his fastball at a 34.9% rate, and his change-up basically was put on the back-burner, dipping to a 4% usage rate.

In Hernandez’s defense, his slider was one of the most effective of its kind in baseball last year. Opponents managed just a .170 batting average, .259 slugging percentage, and .216 wOBA. There were 109 pitchers who threw a slider in at least 100 plate appearances. Hernandez had the 5th lowest opponent wOBA, 9th lowest opponent slugging percentage, and the 20th best run value per-100 pitches. His 39.5% whiff rate was also the 30th best, and was one of just eight pitchers with a strikeout rate over 40% with his slider.

Part of his change in pitch usage is because he faced fewer right-handed batters in the second half compared to the first half, ten less to be exact despite appearing in the same amount of games. But Hernandez may want to become comfortable with throwing his change-up against right-handed batters next year. At the very least, he should play around with the idea in Spring Training. Plus now that the Pirates kept him on their 26-man roster for the entire year, they can send him to Triple-A where he can work on using his third pitch more frequently against right-handed hitters.

I’d also suggest Hernandez to work further up in the zone with his four-seamer. The lefty had a 99% active spin rate and about average ride through the zone with his fastball. Hernandez has some heat on his fastball, and given its ability to fight off gravity, he may be able to get away with a high fastball more often than where he threw it last year, which was typically in the lower-middle part of the strike zone.

I could very much see Hernandez being a potential long term cog in the Pirates’ bullpen. The potential is definitely there. His slider was an elite pitch, and both his fastball and change-up flashed potential. Hernandez needs to get comfortable with throwing his changeup against opposite-handed batters, and trust his fastball more, using it further up in the zone. It has the active spin to work in the top part of the strike zone.