The Astros bullpen has for months been the source of consternation in Houston, as late-inning collapses and general inconsistency have been a factor in the team underperforming expectations. Between recent blown saves by established closer Luke Gregerson and early struggles by high-priced acquisition Ken Giles, manager A.J. Hinch has confirmed he'll implement a closer by committee in coming series.
The candidates? Gregerson, Giles, and perhaps surprisingly, 31-year-old right-handed pitcher Will Harris. Yes, his 0.34 ERA is currently the second-best in the Majors (behind only Fernando Rodney, who has yet to allow an earned run in 21 innings), but he's a former 30-year-old waiver claim who has never demonstrated the fielding independent numbers to back up such production. However, that was until this season.
Led by a 24.7 percent K-BB rate, Harris has a 1.40 FIP and an elite 68.7 percent ground-ball rate in 26.2 innings pitched - there's nothing more one could reasonably ask of a reliever. For context, that FIP is behind only Andrew Miller and is slightly ahead of Dellin Betances among qualified relievers. The 0.00 percent home run rate will not last, but this is still the continuation of positive improvement seen last season, when he pitched to a 1.90 ERA with a strong strikeout rate and a then-career-high 50.7 percent ground-ball rate over a career-high 71 innings.
He accomplishes these numbers using almost exclusively a cutter and curveball. Per Baseball Prospectus, these pitches have featured crazy 66 percent and 76 percent ground-ball rates, respectively, and have generated whiffs at similarly impressive amounts. The cutter has generated 13.0 percent whiffs while earning a 22.4 percent strikeout rate, and the curveball has earned swing-and-misses 17.7 percent of the time and has struck out 45.2 percent of batters.
Harris has some decent stuff - 92.9 mph on a cutter is pretty hard, even for relievers, and the pitch features decent rise as well. The curve features two-plane movement as well, and there exists a 15-inch average difference in vertical movement between the pitches. It's above-average stuff, and a repertoire without a traditional fastball is certainly unusual, but it's not clear from this alone that this is an elite reliever.
What I believe is probably very responsible for the increase in whiffs, increase in ground balls, and significant drop in walks is his command of these pitches. Note the below zone profiles of each pitch against left and right-handed batters, before (2012-2014) and after (2015-2016) Harris arrived in Houston.