Photo Credit: Gregory Bull/AP

Edwin Díaz’s ninth inning last night was the sort of performance that seems to stretch the reasonable connotation of striking out the side when correctly described with the technical definition of the term. All three outs came via strikeout, sure; in between those were two runs that nearly squandered Puerto Rico’s three-run lead over the U.S.

But focusing on the near-blown lead overlooks the best part of the inning—how insanely fun those strikeouts were to watch and how fearsome Díaz can be, particularly when he’s using his slider. The 22-year-old reliever only developed the pitch last summer, when the Seattle Mariners gave him the call-up following their decision to proactively convert him to the bullpen. Switching to relief had always seemed like the logical endgame for Díaz as a prospect, with a fastball that touched triple digits and a set of secondary pitches that he usually struggled to handle. But a new grip for his slider completely changed the pitch, along with his whole approach.

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The power of this pitch isn’t new for anyone who glanced at reliever leaderboards last year; Díaz’s slider was almost entirely responsible for his rookie year K/9 of 15.33. (That’s just behind Dellin Betances, but ahead of Andrew Miller and Aroldis Chapman.) His swinging strike rate was more than 18 percent. And last night, it was on full display. The pitch not only took out both Paul Goldschmidt and Buster Posey swinging on strike three, it made both of them look ridiculous for even trying. Just look at the fastball-slider combination against Posey here, from Rob Friedman’s library:

Via Rob Friedman

Team Puerto Rico is already set for the semifinal after today’s game against Venezuela—which is a good thing, with more guaranteed chances to watch Díaz and this gorgeous pitch.