The Rockies signed Justin Miller in November 2014 to shore up their bullpen. The first year of the pact went great. Miller struck out 10.26 batters per nine innings in 33.1 innings of work in 2015. His 94 mph fastball from the right side didn’t stand out in terms of velocity, but he coupled it with a nice slider that generated a lot of swings and misses. Heading into 2016, he was a candidate to get late inning work in the Rockies bullpen.
Maybe it was relievers being relievers. Maybe 2015 was smoke and mirrors. Maybe he just got worse. But the 2016 version of Justin Miller did not live up to the potential seen in the 2015 iteration.
First, Miller was simply more hittable in 2016. In 2015, batters hit .196 against his fastball and .155 against his slider. In 2016, they hit .324 and .267 against those pitches. One could point to the higher than usual .364 BABIP against to bring up bad luck and explain the changes away (one would also have to do the same with the .244 BABIP against in 2015, which is unusually low and often evidence of good luck), but there’s more to it.
Miller was “more hittable” in that batters hit more of his pitches. The trouble was most evident in his slider. His put away pitch wasn’t nearly as effective generating whiffs this year, 11.81 percent, compared to last year’s 17.07. His BABIP against went up because batters put more of his balls in play.
Let’s add on the fact that his walk rate went from 2.97 per nine in 2015 to 4.22 in 2016, and that he performed much less well in high-leverage situations, and we have the picture of a relief pitcher who went from tantalizing to tatterdemalion in a matter of months.
Miller rejected an outright assignment to Triple-A and declared free agency earlier this month. His time with the Rockies is finished, but he could still surface with another team in need of relief.