How Junior Guerra fits the Diamondbacks bullpen

The first major acquisition of the offseason is signing formerly non-tendered Brewers pitcher Junior Guerra. Guerra was non-tendered by Milwaukee when he was due an estimated $3.5M after a solid year in the Brewers bullpen. Less than a week later, the Diamondbacks swooped in and signed him for $2.55M plus two more years of control for his final two arbitration years should he stick.

Guerra fits the classic mold for the type of pitchers Dbacks GM Mike Hazen has been acquiring: Fastball, Curveball, High Spin rates on both. Last year it was Merrill Kelly out of Korea and this year Guerra, although Guerra will probably spend most of the year in the bullpen. Guerra in the 2019 season was in the 82nd percentile for fastball spin rate and 72 for curveball according to Statcast. His stuff likely ticked up going from the rotation to the bullpen, but has reinvented his repertoire as well as he ditched his slider for a curve. He also features a splitter, which has been an effective 3rd pitch. His stuff profiles as a guy who should stretch the strike zone vertically more than horizontally due to high spin 4-seam fastball with a curveball and splitter as his secondaries.

In 2019, Guerra pitched to a 3.55 ERA although ERA estimators aren’t nearly impressed with his performance. Over 83 ²⁄₃ IP, he delivered a 77/36 K/BB ratio and was average at allowing fly balls to leave the yard, resulting in an FIP- and xFIP- of 101 and 109 respectively. The one elite skill he seems to have is limiting loud contact, ranking in the 94th percentile in exit velocity on Statcast. Guerra was in the Top 10 in fewest Hard Hit Balls (exit velocity > 95 MPH), posting an wOBA of .275 for the season. I expect some regression from that number next season, although his xwOBA from the past two seasons are .314 and .300 and the xwOBA stat isn’t necessarily predictive from year to year.

Guerra is a former starter, so we could see him deployed in differing roles. He could be a more than 3 outs guy in the back-end of the pen or a bridge reliever who can get the ball to the late-inning guys after a short start from the starter. I don’t see him entering the rotation given he could only realistically contribute 100 innings for the team in that capacity.