How JoJo Romero Defied Relief Projections on the World Series Stage
Left-handed reliever JoJo Romero has spent multiple seasons outperforming his expected metrics, anchoring a bullpen role through a World Series run while relying heavily on ground balls and an adjusted pitch mix, Baseball Prospectus reported. More than a decade ago, JoJo Romero was selected by the Phillies in the fourth round (107th overall) of the 2016 MLB Draft, later making his major league debut during the pandemic-shortened season before a Tommy John surgery interrupted his 2021 campaign.
Romero Defies Traditional Regression Metrics
Baseball analytics traditionally treat a pitcher whose earned run average sits significantly below their Fielding Independent Pitching as a candidate for negative regression. Since 2024, Romero has posted a -0.92 difference between his ERA and FIP, ranking him 12th among qualified relievers. Yet that anticipated regression toward the league average has failed to materialize across multiple seasons.
During his early stints with the Philadelphia Phillies, Romero posted a high runs-allowed average relative to his Deserved Run Average, registering a modest 12% K-BB% differential and an acceptable 86 DRA-. Defensive alignment played a role during that initial sample, alongside the hitter-friendly dimensions of Citizens Bank Park, while a ground-ball pitcher was hindered by having Alec Bohm at third base with a -1.8 DRP between 2020 and 2021. Following subsequent trades to the St. Louis Cardinals—where he was exchanged in August 2022 for versatile infielder Edmundo Sosa in a transaction both teams can feel quite satisfied with—and later the Milwaukee Brewers, his performance metrics stabilized as his ground-ball tendencies found a better fit with elite infield defense and the pitcher-friendly Busch Stadium.
Repertoire Adjustments and Pitch Usage Changes
Romero restructured his pitching arsenal, moving away from a four-seam fastball that never had exceptional movement or velocity. In 2021, he utilized a four-seam fastball 35.1% of the time. By 2024, that usage dropped to 10%, and it hit a low of 2% this year. He introduced a sweeper in 2022, maintaining roughly a 37% usage rate from 2024 onward, while his sinker usage climbed to approximately 45% this year to reach a new high alongside his sweeper and a changeup used against right-handers.
This mix provides distinct looks against both left-handed and right-handed hitters, avoiding reliance on overpowering velocity. Across four postseason appearances totaling 5 and 1/3 innings, Romero recorded a K-BB% differential of 42.1%. In Game 4 of the National League Championship Series, he struck out Max Muncy to close out the sixth inning, leaving Kyle Tucker—who was surprisingly the lone consistent Dodgers hitter in the postseason—stranded on third base.
Trade to Milwaukee Leads to World Series Action
Acquired by Milwaukee via trade from St. Louis when executive Chaim Bloom traded the left-hander's expiring contract for prospects, Romero slotted into a relief role. Operating as the second left-handed pitcher in the bullpen, he carved out success through contact management and ground balls rather than pure strikeout totals.
That production carried the left-hander directly into World Series action, marking an unexpected statistical outlier for a reliever who began his career as a mid-round draft pick with modest early returns in Philadelphia.
