Greg Holland has had his hits and misses in the last few years but the former Rockie returned to the Royals in 2020 and had a great season.
Holland, 35 in November, made 28 appearances and pitched to a 1.91 ERA, 2.52 FIP, and an ERA+ of 242. He had a WHIP of 0.953 and nearly a 4.5:1 strikeout-to-walk ratio.
When he was a Rockie back in 2017, he was one of the best relievers in baseball (except for a bad month of August) so perhaps the Rockies could look to bring him back.
Keone Kela is the youngest reliever on this list and he’s the only player on this list that didn’t pitch much in 2020. He was injured for most of 2020 with a forearm injury. If it’s severe enough, it could mean Tommy John surgery.
However, when Kela, 28 in mid-April, is healthy, he is one of the best relievers in baseball. From 2017 to 2019, he pitched in 125 games and pitched to a 2.84 ERA (162 ERA+). His WHIP was 1.014, his FIP was 3.20, and he struck out more than 11 batters per nine innings compared to only 3.5 walks.
Trevor May has been a key to the Minnesota Twins bullpen and making the playoffs in the last two seasons. May, 31, has made 113 appearances since the start of the 2018 season and he has pitched to a 3.19 ERA (140 ERA+) and a FIP of 3.56. His WHIP is in that span is 1.08 and he has struck out more than 12 batters compared to only 3 walks per nine innings.