This is one in a series of stories breaking down members of the Pittsburgh Pirates’ 40-man roster.

Jose Hernandez had two distinctly different halves of his rookie season, which leaves questions about whether the left-hander can become a long-term member of the Pittsburgh Pirates’ bullpen.

Hernandez looked like a Rule 5 steal before going on the injured list on June 18 with a right calf strain. Selected from the Los Angeles Dodgers at the Winter Meetings, he had a 0.77 ERA in nine games through the end of April and his ERA was at 2.63 in 26 games when he was injured.

Yet Hernandez struggled after returning on July 21. He posted a 7.71 ERA and 1.75 WHIP in 24 games the rest of the season despite having 34 strikeouts in 23.1 innings.

Overall, Hernandez concluded his first major-league season with a 1-3 record, a 4.97 ERA and a 1.36 WHIP in 50 games. In 50.2 innings, he struck out 62.

As part of the Rule 5 Draft process, the Pirates were forced to keep Hernandez on their major-league 26-man roster all season or else would have had to offer him back to the Dodgers. The Pirates will now be able to freely option Hernandez to the minor leagues in 2024.

The personable Hernandez has shown he can be an effective major-league pitcher as evidenced by his first-half results, including stringing nine consecutive scoreless outings covering 9.2 innings together from May 17-June 14.

There were other encouraging signs, including opponents having just a .170 batting average against his slider, which Hernandez threw 55.9% of the time. He also ranked in the 80th percentile among major-league relievers in strikeout rate, 78th in hard-hit rate allowed and 73rd in whiff rate.

Conversely, Hernandez was in the 25th percentile in chase rate and 28th in walk rate. Opponents also hit .346 against his changeup and .322 off his four-seam fastball.

So, who is the real Jose Hernandez? The guy who had such a good first half or the pitcher who struggled after the All-Star break while possibly still feeling the effects of his calf injury?

Hernandez, who turns 26 on New Year’s Eve, has a big arm with a fastball that reached 100 mph when he was in the Dodgers’ organization and averaged 94.6 mph last season. He also has the slider, which can be a wipeout pitch.

However, Hernandez is not a lock to be on the opening-day roster in 2024. Ryan Borucki seemingly has the edge for the top left-handed relief spot, meaning Hernandez’s chances of making the team in spring training will likely depend on how he fares in Grapefruit League action.

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