Jeremy Jeffress was one of the NL’s best relievers in 2018, when he was named to the All-Star team and finished with a 1.29 ERA and 2.78 FIP. But the former Brewer followed his successful season with a 5.02 ERA and 3.96 FIP in 2019. What was the major difference between Jeffress’ disparate performances?
The one number that best explains his underwhelming 2019 is a sudden decline in whiff rate. Jeffress dominated in 2018 with a 30% whiff rate, which means he was inducing a swing and miss nearly once every three swings. But in 2019, that rate had dropped to a 20% mark that was the righty’s lowest since his tenure with the Blue Jays in 2013.