Brayan Bello's Unprecedented Shift from Starter to Reliever

As MLB.com first reported, Boston Red Sox pitcher Brayan Bello has produced a statistical swing unheard of in baseball history. After struggling as a starter with a 10.35 ERA—making him the least effective starter in the league—Bello has transitioned into the most effective reliever in baseball with a 0.85 ERA.

MLB.com reports that no pitcher in history has ever performed this poorly as a starter and this well as a reliever in a single season (based on a minimum of five starts and 30 innings in each role). The disparity remains stark even when accounting for expected ERA; Statcast calculates Bello's expected ERA as 8.42 as a starter compared to 3.34 in relief.

The shift in performance is mirrored by a drastic change in efficiency. As a starter, Bello posted a 12% strikeout rate and an 11% walk rate while allowing 2.5 home runs per nine innings. In relief, his strikeout rate jumped to 23%, his walk rate dropped to 4%, and he surrendered only one home run across 52 2/3 innings, MLB.com reports.

While his overall "Stuff+" remains identical, MLB.com notes a significant jump in "Location+," which rose from a 98 as a starter to 114 as a reliever. Specific improvements include a reduction in four-seamers thrown in non-competitive areas (from 50% to 31%) and better cutter placement against left-handed hitters. When asked about the transition, Bello told MLB.com, "It's working."