Although Alec Mills had many a handful of starts for the Chicago Cubs before last season, 2020 was the first year he got an actual dedicated spot in a rotation. This season, however, he opened up as the long-man/swing man in the bullpen. Much to my surprise, to be honest.
Sure, the overall results weren’t great last year (4.48 ERA, 5.10 FIP), as he struggled mightily against left-handed hitters, and he could/did provide value in the bullpen. But this was still a 29-year-old starter under cheap team control through 2025, who threw a no-hitter and finished as a finalist for the 2020 NL Gold Glove award. I just kind of assumed the Cubs would give him a shot. Instead, they went with Kyle Hendricks, Jake Arrieta, Zach Davies, Adbert Alzolay, and Trevor Williams, perhaps knowing that Mills would get his chance at some point due to injuries, ineffectiveness, and trades. And, hey, it happened!
After a spot start earlier in the year, Mills joined the Cubs rotation on June 15th, and has already made nine starts. Nine pretty dang good starts, I might add, including last night’s strong effort against the Rockies at Coors Field: 6.0 IP, 8H, 2ER, 2BB, 3Ks.
Compared to all qualified MLB starters during that stretch, Mills 3.55 ERA ranks 32nd, his 3.41 FIP ranks 19th, and his 1.0 WAR ranks 23rd. That is a pretty notable slate of statistics. So how is he doing it? Well, in classic Mills’ fashion, he isn’t striking many batters out (17.9%), and that’s not great, but he’s also done a great job at limiting the free passes (6.1 BB%) and a great job keeping his contact on the ground (53.5%). In fact, that groundball rate ranks 5th in MLB during that stretch.
But that’s not what we’re here, today, to discuss.
Much like Patrick Wisdom and his strikeout rate, the one thing holding Mills back from being a sure-fire back-of-the-rotation starter is his performance against left-handed hitters. But also much like Wisdom, he’s taken some strides in that department since the middle of June.
To really understand how far he’s come, let’s start with last season.
Against Mills in 2020, lefties hit a ridiculous .275/.338/.551 (.374 wOBA) with 10 homers and a minuscule 14.6% strikeout rate. Knowing that, most teams could just load up on lefties and expect some success before the 5th inning rolled around. And success, they found: 6.06 ERA.
But against lefties as a rotation starter this season, Mills has shaved 24 points off his wOBA, .272/.359/.444 (.351 wOBA), with an ERA equivalent of 4.43. And before having to pitch at Coors last night, it was even better: .250/.333/.403 (.324 wOBA).
And that’s not all. Here are some comparisons against LHH from 2020 to this rotation stretch in 2021:
It’s certainly not all good news, but he’s striking out more lefties, he’s generating more ground balls, and he’s allowing fewer hard hits. That’s progress. And maybe that’s not enough for you to be convinced of his future in the Cubs rotation, but remember: (1) lefties are his kryptonite and always will be, so any progress is a good sign, (2) there are far fewer lefties in most lineups than righties, and (3), hey, he’s also quietly killing it against right-handed batters!
In that same stretch against righties this year, Mills has a 2.84 ERA, allowing just a .300/.320/.370 (.302 wOBA) slash line. He’s striking out 18.3% of the righties he faces while walking less than 3%! Meanwhile, righties can’t do a lick to elevate against him (60 GB%) and they’re making a ton of soft contact (22.0%) and very little hard contact (30.5%).
Given our expectations for him as a back-of-the-rotation starter with solid defense on the mound and multiple years of cheap team control … man, you can do a WHOLE lot worse.
With Kyle Hendricks and Adbert Alzolay already penciled into the 2022 rotation, and Justin Steele and Keegan Thompson perhaps on the way, Mills probably hasn’t done enough just yet to lock himself into the next Cubs rotation – and, indeed, he may always provide more value as a swing guy, anyway – but he’s certainly on his way. And if he continues to improve against lefties over the course of the season while stepping on the necks of righties along the way, it’s going to be hard not to want him in that 4th/5th slot next year. Like I said, the Cubs could do a whole lot worse.