It was announced on Monday that Carlos Martinez will be returning to the Cardinals rotation and Kwang-Hyun Kim will be occupying a high-leverage role in the bullpen. With Martinez’s history of success and Kim’s impressive Spring Training and Summer Camp outings since coming over from the KBO, it seems as if the Cardinals did not have a bad option. Now with Martinez returning to his former role as a starter and Kim heading to the bullpen, it seems that the Cardinals have solidified their pitching staff, and it could be a very good one in 2020.
Carlos Martinez racked up 9.7 fWAR in the starting rotation from 2015 to 2017 before moving to the bullpen at the end of the 2018 season. These consistently solid results were crucial to the Cardinals pitching staff in those years as Martinez was able to provide quality pitching for a large amount of innings (580 IP from 2015-2017). It may be optimistic to hope for Martinez to return to this level of production, but given his solid performances in the bullpen, it does not seem impossible. It will take an adjustment for Martinez to begin throwing longer stints during games, but he showed last season that he is still a very good pitcher.
In the bullpen last season, Martinez had a career high strikeout rate (9.87 K/9) while maintaining his walk rate from the previous season. Additionally, over the last two seasons, Martinez has slashed his HR/FB% from an average of 12.5% from 2015-2017 to an average of 5.3% over the last two seasons. Even with the injuries that he has suffered, he has clearly not lost his effectiveness. Even though it is generally easier to pitch out of the bullpen, Martinez showed an ability to handle high leverage situations and his success can only bode well for his future, even if his future is in the rotation instead of the bullpen.
Additionally, this will be the first time that the Cardinals will have a full, albeit abbreviated, season of Jack Flaherty and Carlos Martinez in the rotation. If Martinez is able to experience similar levels of success this season as he did in 2015-2017, and Flaherty continues to be Flaherty, then the Cardinals appear to have two solidly above average starters with potential to be much better. Additionally, it does not seem like Mikolas will be a worse pitcher than last season when he posted 2.5 fWAR in 184 innings. If anything, he could improve if he could return his home run rate to his 2018 levels. His home run rate nearly doubled, from 0.72 HR/9 in 2018 to 1.32 HR/9 in 2019 while his strikeout rate and walk rate both increased slightly as well. The biggest difference between 2018 and 2019 for him was the spike in home run rate and that appears to be the cause for his rise in FIP from 3.28 in 2018 to 4.27 in 2019. If he could lower his home run rate then Mikolas could also see his numbers improve this season.
Adam Wainwright is not getting any younger and Dakota Hudson’s underlying statistics last season were not encouraging, so it would not be surprising to see either or both of these pitchers decline this season. However, even if that happens, there is the possibility for the Cardinals to have an above average rotation and maybe even sneak into the top ten due to the ceilings of Martinez, Flaherty, and Mikolas. However, Paul Sporer of Fangraphs ranked the Cardinals starting rotation as the 16th best in the league. Maybe the Cardinals do finish the season with a below average starting rotation, and this could certainly happen if Martinez struggles, Mikolas does not improve, and Hudson and Wainwright decline. However, the potential for this rotation to be solidly above average is also high, especially, if Martinez can return to the rotation nearly as strong as when he left it.
The Cardinals starting rotation finished 14th in FIP in 2019, making them a slightly above average rotation. However, with Martinez returning to the rotation in 2020, there is even great potential for this rotation.