Zach Britton's quiet transformation from failed starter to Orioles closer

It has become a routine for Britton to enter the game in the ninth with the O's in the lead. This would be difficult to imagine even a year ago, but Britton has transformed himself so quickly and so drastically that it has long passed the point where his performance can be considered a fluke. So what exactly has changed for Britton that made him an elite reliever overnight?

As was the case when I examined Britton's change last April, the most important change Britton has made since transitioning to relief is abandoning his four-seam fastball altogether. He has also removed changeups from his repertoire. The result is that he throws his sinker about 90% of the time and his curveball the other 10% of the time. This is the benefit of pitching in relief. Britton only has to face each batter at most once, so he does not to vary his pitches as not to become predicable the second time through the order. Below is his pitch usage from Brooks Baseball.

Britton's sinker is much more effective than his four-seam fastball, as evident from his improvement over the last two seasons. However, there were signs even when he was a starter that he should throw his sinker more and his four-seam fastball less. Below is the result of his pitches by pitch type before 2014 from Brooks Baseball.

His sinker outperformed his four-seam fastball in almost all aspects. His sinker even generated more swing and misses than his four-seam fastball. Maybe if he has given up his four-seam fastball earlier he would still be a starter now. The dominant use of his sinker has led to him leading the league in groundball rate for both last season and this season among qualified relievers.

Of course, there are other reasons behind Britton's success as a reliever. He has thrown more pitches in the zone, leading to batters becoming more aggressive against him. At the same time, batters are making less contact with his pitches. Below is the pitch discipline stats from Fangraphs.

This can be the result of improved command for Britton and his increased velocity (from 93 mph to 96 mph for his sinker) pitching in relief. The improved command and stuff have been reflected in his rising strikeout rate and declining walk rate, both of which are trending in the right direction this season.

Britton has maintained what made him so unhittable last April for more than a year. It is no longer a small sample size and we should be glad that the O's did not give up on him sooner like a lot of fans did.