Welcome to the 2019 edition of Ranking the Rockies, where we take a look back at every player to log playing time for the Rockies in 2019. The purpose of this list is to provide a snapshot of the player in context. The “Ranking” is an organizing principle that’s drawn from Baseball Reference’s WAR (rWAR). It’s not something the staff debated. We’ll begin with the player with the lowest rWAR and end up with the player with the highest.
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No. 11, Jairo Diaz (0.7 rWAR)
Since coming over from the Angels in a trade for Josh Rutledge after the 2014 season, Jairo Diaz has always been something of a big “What if...” for Rockies fans.
In 2019, that “What if...” became a reality, as Diaz finally put in a significant number of big league innings, posting a 4.53 ERA and 3.70 FIP in 57 2⁄3 innings and 56 appearances, walking 19 and striking out 63. He also earned his first five career saves, filling in as the closer late in the season after Scott Oberg’s injury.
Through Diaz’s first four years with the Rockies, he pitched just 24 innings in the majors thanks to a variety of injuries, including undergoing Tommy John surgery in 2016. Finally healthy this season, Diaz was able to take the opportunity given to him when other relievers got hurt or under-performed.
Diaz’s 4.53 ERA in 2019 may not look good on the surface, but his peripherals were excellent. He struck out 25.7% of the batters he faced, walking just 7.8%, both quite solid. Diaz also found himself in the 75th percentile of pitchers in xwOBA and the 77th percentile in xSLG, per Baseball Savant.
The tantalizing thing about Diaz with the Rockies has always been his high-octane fastball, which averaged 97.3 MPH in 2019. However, his success came from pairing that fastball with a wipeout slider. Diaz threw his slider more than 40% of the time this season, getting a whiff rate on it of 46.9%, allowing hitters to hit just .189 against it, and recording 50 of his 63 strikeouts on the season on his slider.
Provided he’s healthy, Diaz should factor into the late-inning mix for the Rockies in 2020 along with Oberg and Carlos Estevez, among others. For 2019, it was nice to see what had been a long-time question for Rockies fans finally answered.