When analysts first tried to measure how much a reliever’s work was diluted by the runners left on base, they stumbled upon a quirky adjustment called RE‑RA9. The metric tweaks traditional run‑average figures by stripping out the influence of inherited runners, giving a clearer picture of a pitcher’s true impact.
Building on that foundation, a recent FanGraphs study broadened the data set to span decades, pulling in seasons that pre‑date the modern bullpen era. By doing so, the authors could spot patterns that had long been hidden behind raw save totals.
Among the names that surfaced, three Hall‑of‑Fame‑caliber closers — Jesse Orosco, Trevor Hoffman and Mariano Rivera — stood out for their ability to keep inherited runners from crossing the plate. Their careers show that even the most dominant late‑inning arms can be judged more fairly when the inherited‑run component is accounted for.
The investigation also turned up a single‑season outlier that still reverberates through the statistics: the 2016 campaign of Zack Britton. That year the Baltimore Orioles reliever posted the greatest relief‑season performance ever recorded under RE‑RA9, a testament to how a well‑timed setup can reshape a team’s late‑game strategy.
Beyond the headline names, the article highlights a handful of lesser‑known arms — Rollie Fingers, Dan Quisenberry, Kent Mercker, and others — who either excelled or faltered when the inherited‑run filter was applied. Their stories illustrate how the metric can both elevate overlooked contributors and expose vulnerabilities in otherwise reliable relievers.
Why RE‑RA9 Matters for the Next Generation
As front offices increasingly lean on advanced analytics, RE‑RA9 offers a template for future evaluation tools. Its emphasis on context rather than raw counts suggests that the next wave of pitcher assessment will be rooted in a more nuanced understanding of game flow.