The St. Louis Cardinals are traditionally a strong pitching team with plenty of depth that is ready to step up if needed. That is not exactly true this season. Even though the Cardinals had players like Daniel Ponce de Leon, John Gant, Carlos Martinez ready to step into the rotation, they had not performed as well as needed.
John Gant has performed the best of the three with an ERA of 2.25 and a FIP of 4.04. However, his xERA and his xFIP are much worse at 5.78 and 4.80, respectively. Additionally, he has averaged just five innings per start with a walk rate just under 15%. Ponce de Leon was removed from the rotation when Kwang-Hyun Kim returned from injury, which allowed the Cardinals to improve in the rotation. Ponce de Leon has compiled a 9.64 ERA and 8.24 FIP in just 9 1⁄3 innings this season. In his second, and final (so far), start in the rotation, Ponce de Leon was unable to escape the second inning. Carlos Martinez has struggled as well, as he has posted a 6.00 ERA and 5.92 xERA. His FIP and xFIP are better at 4.09 and 4.69, but he still has accumulated just 0.3 fWAR in four starts this season.
Overall, these three have combined for 0.3 fWAR through 20 games. That is simply not good enough from the final three spots in the Cardinals’ rotation. With Kwang-Hyun Kim added to this group, that number rises to 0.6 as his 4.15 ERA and 2.52 FIP through two starts have been a significant boost to the rotation.
Now that Kim is back, and pitching better than Ponce de Leon in the rotation, it seems that John Gant and Carlos Martinez are competing for the final rotation spot once Miles Mikolas gets healthy. This is a huge benefit for the Cardinals, and the team will see its rotation improve significantly when both Kim and Mikolas are pitching deep into games. Ponce de Leon, Gant, and Martinez all profile better as relievers at this point in their careers, so having all three of them in the rotation at the same time was a challenge. They all kept the Cardinals in some games, despite not pitching well as a whole and putting a heavy burden on the bullpen.
Miles Mikolas should be able to do better than that. He is a proven innings eater who threw over 200 innings in 2018 and 184 innings in 2019 while compiling 6.7 fWAR between the two seasons. This is something that the back of the Cardinals rotation lacks. Flaherty and Wainwright (sometimes) are capable of pitching deep into games when the bullpen needs a rest, but the back end of the rotation was not able to consistently do this.
Through 20 games, the Cardinals starting rotation ranks 21st in innings pitched (97), 23rd in ERA (4.73), 18th in FIP (4.18), 27th in xFIP (4.54), and 22nd in fWAR (1.1). These are not numbers that are worthy of a team that is competing for a division crown and a playoff spot. The rotation did enough for the team to be in second place in the NL Central with a 10-10 record, but without the reinforcements of Kim and Mikolas, the rotation likely would not have been able to last to the all-star break without any acquisitions.
This is unusual for the Cardinals, who usually have plenty of starting pitching depth in the minor leagues. However, the Cardinals clearly felt more comfortable with MLB relievers who have a history of starting than with prospects like Johan Oviedo and Jake Woodford. Part of this problem may be due to the fact that there was not a minor league season last year. Due to this, Oviedo has yet to appear above Double-A and Jake Woodford has yet to post strong results in either Triple-A or the major leagues.
However, this is also a sign that the Cardinals are lacking in upper level pitching depth. They have acquired plenty of young pitchers in the last few years, but they are still in the lower levels of the minor leagues. Because of this, the Cardinals were forced to use pitchers like Ponce de Leon, Gant, and Martinez in the rotation. It has not killed the team as the Cardinals are still at .500, but it is clear that the rotation needs Miles Mikolas back as soon as possible.