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.

Clearly, it seems that Will Harris has one of two goals when he throws a pitch - either throw a cutter away from the batter or throw a curveball down and to his glove side. He's gotten a lot better at doing both of those things since joining the Astros, particularly with cutters against lefties. He can work both sides of the plate with the pitch and generates a lot of high swings-and-misses against batters of both hands.

This seeming simplicity in approach extends to his pitch usage - when the batter is ahead or the count is even, expect a cutter. When Harris is ahead, the odds of a curveball are closer to even. This is a pitcher with above-average stuff, throwing seemingly predictable pitches to predictable locations in predictable counts - is it safe to say that he won't end the season as the fourth-best reliever in baseball?

Probably. He's at least going to allow a few home runs and come back closer to Earth, but he'll go roughly as far as his command will take him. Well-placed pitches with movement are really difficult for batters to hit, even when they know what is coming (see Rivera, Mariano). However, relievers are notoriously inconsistent, and aside from having elite stuff (see today's Yankees bullpen) it is really hard to predict who will be good a month from now. If he lost his command tomorrow, he'd no longer be effective. However, Harris has performed exceptionally through one and a third seasons with the Astros and has earned the opportunity to pitch in high leverage situations. It's up to him to take it from there.

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