How will the Cubs fill out the back end of the starting rotation?

Chicago Cubs will have to see how options shake out come spring

Starting with Alzolay, he may present the biggest conundrum of the four. While he’s shown exceptional ability to miss bats (career K/9 of 9.6), his struggles against lefties are well documented, and unless he dramatically improves in this area, he likely won’t survive as a starter.

Working with Alzolay to try and improve his approach against lefties should be a top objective for the team once the lockout ends. The young right-hander has flashed brilliance as a starter, but he’s also looked unhittable in stints as a reliever, and if he doesn’t show improvement, his future may be in the bullpen.

Mills is another candidate for the rotation and he’s certainly the most seasoned of the candidates. Though he’s not an exciting option, he’s been reliable as a fifth starter or as a swingman in the past, which is something that could endear himself to David Ross.

The issue with Mills is that he’s not a strikeout pitcher whatsoever, instead relying on soft contact. The additions of Miley and Stroman made the Cubs’ top three rotation spots all reliant on soft contact, so they’d likely want to get a different type of pitcher at the bottom of the staff.

If the Cubs want a strikeout pitcher in the mix, they’d be wise to give Justin Steele a look. Steele is a similar style of pitcher to Alzolay as he has a very good strikeout rate (K/9 of 9.3), but also gets burned by the longball (HR/9 of 1.9). However, after some rough outings early on as a starter, Steele turned his season around, flashing real potential of being a long-term starter.

It’s also important to note that Steele underwent a massive role change in the middle of the season. After impressing out of the bullpen early in 2021, the Cubs decided to stretch him out into a starter for after the break. Despite some early growing pains, Steele looked like he belonged for a good stretch of the season, and should get another look.

Chicago Cubs could stick internal or look for a buy-low free agent option

The final realistic candidate for the rotation is Keegan Thompson. Like Steele, Thompson was stretched out after an early bullpen stint and was added to the rotation after the trade deadline. Thompson also had a K/9 of 9.3 but struggled mightily with walks, posting a BB/9 of 5.2.

Thompson began to struggle both out of the bullpen and in the rotation, looking more and more fatigued as the season wore on. The righty is likely a long shot to start the season in the rotation, but there is some potential with him, and some refinement in the minor leagues will likely be the best path for him to start the year.

The final two spots in the rotation could go any which way, and while it’s possible the Cubs add a cheap free agent, it seems more likely that they’ll rely on in-house options to fill the void. All four will have the opportunity to make their cases at spring training, and Ross and Hoyer will certainly be watching closely.

While many may think Mills could be a favorite for one of the spots, Hoyer has repeatedly stated the need for power pitchers in the rotation, which certainly favors Alzolay, Steele, or even Thompson over Mills.

However, spring training will be massive for Alzolay, and if he doesn’t show improvement against lefties, it’s unlikely he starts the season in the rotation. It’ll certainly be a compelling battle to watch, and it could go any number of directions.