Rangers' opener strategy may not be enough to unlock Kumar Rocker's potential

Texas Rangers right-hander Kumar Rocker has been outstanding in two games following an opener this season, recording a 1.42 ERA with 16 strikeouts over 12 2/3 innings. While some may deduce that Rocker's success in those two appearances was due to him not starting, a deeper look at the situation reveals he upped his slider usage in the two outings and benefited from it.

Not to say it would be a bad strategy for manager Skip Schumaker to continue using an opener before Rocker, given the 26-year-old right-hander's success in those situations, but his increased slider usage seems to be the real reason he has found success pitching after an opener. This season, Rocker has thrown his slider 38.9% of the time on average.

But on May 19, following an opener against the Colorado Rockies at Coors Field, he increased the usage to 43% and threw 7 2/3 scoreless innings. He upped his slider usage even more following an opener against the Miami Marlins at LoanDepot Park on Monday night, throwing it 51% of the time with a 74% whiff rate en route to collecting a career-high nine strikeouts on 76 pitches across five innings.

Kumar Rocker's slider is clearly his best pitch, and the Rangers' opener strategy has given him the confidence to unleash it

It seems Rocker would benefit from continuing to increase his slider usage. This year, the pitch has induced 39% whiff and strikeout rates with a .171 opponent batting average and +7 run value. While his slider is his most-used pitch this year, throwing it around half the time as opposed to about 39% could lead to more success for Rocker.

Rocker's four-seamer (10.6% usage) and changeup (6.4%) have also been effective, while his sinker (31.9%) and cutter (12.4%) have been hit hard. Rocker shouldn't completely cut out his sinker and cutter, but he should consider using them at a lower rate while upping his slider usage.

Overall, Rocker has posted a 4.14 ERA (4.05 FIP) with a 20.2% strikeout rate (35th percentile) and 9.3% walk rate (39th percentile) this season. He also has a lowly 43.3% hard-hit rate (19th percentile) and 89.7 mph average exit velocity (29th percentile). On the bright side, his 47.8% ground-ball rate ranks in the 74th percentile.

The 26-year-old has been one of the key players in Texas pitchers' first-inning woes. As a starter, he's given up 16 earned runs over 26 2/3 innings pitched (5.40 ERA) when navigating the batting order for the first time, many of which have come in the first inning of his starts.

It appears that by following the opener and skipping the top of the opposing team's batting order his first time through, Rocker is able to quickly build confidence and dictate what he wants to do by leveraging his best pitch more frequently. Rather than working on establishing the fastball, he's not thinking as much and is simply throwing his most effective offering at a greater frequency.

Once a top prospect, Rocker is still trying to live up to his potential as the third overall pick in the 2022 draft. He had a disappointing 2025 season with a 5.74 ERA over 64 1/3 innings, and his overall numbers this year aren't great. Spamming his slider could be the key to unlocking the best version of himself.

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