21) German Marquez’s 2017 season (Age 22 season)
2017 was also German Marquez’s rookie season and he was really close in rankings with Freeland and our next spot for a few reasons but Marquez slots in the middle for a few reasons.
He went 11-7 with a 4.39 ERA, a 4.40 FIP, and a 115 ERA+ while averaging 8.2 strikeouts and 2.7 walks per nine innings. He came in 5th in NL Rookie of the Year voting and he had a 3.6 WAR.
Like Freeland, he faded as the season progressed as in his final 10 starts, he went 2-3 with a 5.43 ERA. Batters hit .323/.366/.595 against him in that span too.
20) Jon Gray’s 2017 season (Age 25 season)
Jon Gray was the Rockies ace in 2017 but he isn’t ranked higher or even as the top Rockies starter at or under the age of 25 from that 2017 season for one main reason and it’s the main issue of Gray’s MLB career: injury.
Gray, who turned 25 the previous November, went 10-4 with a 3.67 ERA in 20 starts. In 110 1/3 innings, he struck out 112 batters while walking just 30 (9.1-to-2.4 strikeout-to-walk ratio) with a 3.18 FIP, a 138 ERA+, and a WAR of 3.0. He ended up receiving the start for the Rockies in the 2017 Wild Card game against Arizona and he was bombed in what, to date, has been his only postseason game.
In 1 1/3 innings, he allowed seven hits and four runs (all earned) before he got pulled in favor of Scott Oberg in the Rockies eventual 11-8 loss.
Not a great way to end the season but his season was still is good enough to get on our list and top our list for the trio of Rockies starters under the age of 25 in 2017. Despite pitching 50 fewer innings, he was the best of the trio and that’s why manager Bud Black turned to him in the Wild Card game.