As I reflected on Alec Mills’ amazing Sunday, I couldn’t help but juxtapose his current brilliance with how close he may have been to getting designated for assignment last year.
It was late May 2019, Mills was the Iowa Cubs’ worst-performing starter with an ERA in the eights, and he had already used his last minor league option (and so would be out of them for 2020). On the 40-man roster around that time, there was probably a week or two when he was clinging to the final spot.
It was around then that I noticed Mills was messing around with a new (way to throw a) pitch. He’d shown it some before, as I recall, but it was around summer when it became a fully entrenched part of his arsenal:
Alec Mills newish 65 mph curveball.
I like to think of me as the batter, Mills as Monday morning and the ball as the alarm clock. pic.twitter.com/IG28JvXuIQ
— Cubs Prospects – Bryan Smith (@cubprospects) July 8, 2019
Always good for a chuckle. But also, wow has that pitch made a difference to the whole arsenal. With its addition, Mills now throws pitches in virtually every part of the 65-92 mph range, and has enough to work with to keep hitters off balance even without premium velocity or stuff.
As Michael Ernst at Cubs Den noted today, Mills threw the slow curve 23 times yesterday. Functionally, Mills uses the pitch as a main offering against left-handed hitters, throwing it 20% of the time (versus just 7% against RHH). Mills is putting up with lefties this year (.243/.311/.460), where he’s dominating righties to the tune of a .150/.225/.263 batting line allowed.
Still, though, it’s worth recognizing that we’re only about two starts removed from questioning whether the rotation was the best fit for Mills after all. Mills is one of those pitchers who lives with a very thin margin for error, with very little separating good starts from ugly ones. He’s not gonna walk a lot of guys, or get a lot of strikeouts. Instead, his success or failure will depend largely on good old fashioned “how hard is he getting hit?” The tiniest variation in command, like with Kyle Hendricks, can create a huge change in results.
Mills’ continued development will simply be working to reduce the number of times he’s hit hard, and figuring out what he might want to tinker with to achieve that.
I looked on Baseball Savant for every pitch this year that Mills has thrown that has ended up with a ball in play that has a .500 xwOBA or better (i.e., a ball that was hit very, very well). It has happened 37 times on 788 total pitches, good for 4.7% of the time, in line with where it’s been for his whole career. Of those 37 balls in play, 24 were against left-handed hitters, versus just 13 for right-handed hitters. Here’s the breakdown by pitch type:
Four-seam against LHH: 8 times
Four-seam against RHH: 4 times
Sinkers against LHH: 8 times
Sinkers against RHH: 8 times
Curveballs against LHH: once
Curveballs against RHH: once
Sliders against LHH: zero
Sliders against RHH: zero
Changeups against LHH: 7 times
Changeups against RHH: zero
In fact, I want to note, Mills has not given up a hit on a change-up to a righty this season, despite having thrown 50 of them. He’s also given up just one hit on a slider against either batter type. I wonder if we might see the slider usage increase over time, as it has been his most effective pitch (though some of that may be due to how seldom he throws it, of course).
There are two pitch types here that jump out to me as places that Mills should be able to shore things up a bit. The first would be the four-seam fastball against left-handed hitters when ahead in the count. Mills has thrown a left-handed hitter a two-strike four seamer 26% of the time this year, and lefties have a .588 slugging percentage in that scenario. It hasn’t even been a problem of execution, as Mills has succeeded in avoiding the middle of the zone. It’s just a pitch liable to getting tattooed. I wonder if the Cubs might have him start throwing it when ahead a little less often.
The other issue this year, surprisingly, has been Mills’ changeup to lefties. Once his best pitch for neutralizing lefties, this year it’s been slugged around pretty good (.579). I don’t even really have a solution for this issue, but I bet it’s something that jumps out to Mills and Tommy Hottovy. Whether it’s working up a second variation of a changeup (like Kyle Hendricks did) specifically for lefties, reducing its usage, or merely working on better execution, I think this is an area where Mills can get even better.
The Cubs and Mills have done so well to get him to this point, and, given the openings coming next year, you’d just love to see him continue to be a viable starter for this rotation going forward. Because when it works, it’s a balancing act that’s sure fun to watch.