Left-hander Andrew Miller began his career as a starting pitcher with the Detroit Tigers as a 21-year-old in 2006. Things did not go well in that role, as he compiled ERAs of 5.63, 5.87, 4.84, 8.54 and 5.54 in five seasons as a full and part-time starter.

So it made sense that, at 27 years old, the Boston Red Sox decided to stop trying to force a square peg into a round hole and moved him to the bullpen. Since 2012, he has flourished in that role, compiling a 2.62 ERA in 155 games as a relief pitcher (127 innings), striking out 188 hitters and walking just 56 during that time.

This year has been no different, with Miller joining Baltimore after 56 very effective innings with Boston. Overall, this season, his K% of 40.5% is third-best among all MLB relievers, with a 14.3 K/9 rate that is 2nd-best. His nERD of 1.15 is fourth-best among the relievers listed here and his rWAR of 3.3 is 2nd-best, thanks to his 2.09 ERA.

As Baltimore builds a 10-game lead in the American League East, their bullpen has been shored up in a big way by the mid-season addition of Miller to their bullpen.