Aaron Bummer went from having a very limited role for the Chicago White Sox to now holding a key role in their bullpen as he has become one of their best relievers in 2019.
The southpaw entered the season with a career 4.36 ERA, 3.94 FIP, and 1.453 WHIP in 53 2/3 innings (67 appearances) over his first two seasons in the league. That went along with a pretty high walk rate of 4.2 BB/9 as compared to 8.7 K/9.
However, he did show improvement in the walks category in 2018, lowering the rate down 2.