One of the things the Rockies desperately needed and lacked in the 2020 season was a left-handed reliever. They used James Pazos and Phillip Diehl in that role but by the half way point of the season, the Rockies had nine-man bullpen and neither Pazos or Diehl were on it, meaning it was a bullpen of nine right-handers.
Jose Alvarez, 32 next May, averaged 67 appearances a season from 2015 through 2019 for the Angels and the Phillies. He pitched to a 3.36 ERA in that span (123 ERA+) and a FIP of 3.56. He had a WHIP of 1.308 and he struck out more than 8 batters and walked less than three batters per nine innings.
He pitched well in 8 games for the Phillies in 2020 (1.42 ERA and 2.72 FIP) but his season was cut short due to what was later called a “testicular contusion” after a 105 MPH liner hit him in that area.
The Rockies have seen Pedro Baez in his time with the Dodgers and he has been one of their most reliable relievers.
Since 2016, the right-handed Baez, 33 in March, has not posted a season with an ERA+ below 132 and, obviously with the exception of the shortened 2020 season, he has appeared in 52 or more games in each season in that span as well.
Anthony Bass was the playoff-bound Blue Jays closer for most of 2020.
Along with his 2019 campaign with the Mariners, Bass, 33 in November, has been a very good reliever. Since 2019, he has had an ERA of 3.54 in 70 regular season games. He has had an ERA+ of 124, a WHIP of 0.991, a FIP of 3.80, and a 2.5:1 strikeout-to-walk ratio.