Greg Holland was an All-Star for the Rockies in 2017 when the Rockies, in reality, last had an above-average bullpen. He led the NL in games finished and in saves for the Rockies, who made it to the playoffs for the first time since 2009.
He was, arguably, the best reliever in baseball if not for the month of August that skewed his season stats big time.
In 2020, Holland is with the Royals for his second tenure for the team and he has pitched fairly well. He has an ERA of 3.65 in 12 1/3 innings with a WHIP of 1.378, 4.4 walks per nine innings, and 8.0 strikeouts.
The Rockies do have a history of acquiring Royals relievers (e.g. Holland for the first time and Wade Davis) and that’s partially due to their familiarity with Rockies pitching coach Steve Foster, who was the bullpen coach (and, later, a special assistant) with the Royals before he joined the Rockies.
Would Holland be the pitcher that the Rockies had in 2017? Probably not. But he (and Rosenthal) would provide the Rockies with some more bullpen depth for cheap (both salary- and trade-wise).