Willy Adames's Fastball Folly and the Future of the Brewers Lineup

It was an uneven season for Willy Adames. As much as his consistent defense at shortstop meant to the team, his streaks and slumps at bat added to the Brewers' difficulty in generating runs. Adames hit .217/.310/.407 on the year, which constituted a slight uptick in OBP from 2022 but a major power outage. His hard-hit rate plunged, and for a full two months--May and June, combined--he batted .175/.249/.331, striking out 27.4 percent of the time.

Around that, though, Adames was still a pretty productive hitter. He had a .780 OPS in April and a .772 mark from July 1 through the end of the season. Once you account for the fact that he missed a chunk of time during the ugly stretch of his season after being struck in the head by a line drive, it's tempting to say that Adames was his usual self, and that his prolonged period of struggle was just a blip. 

There's one problem there, though: Adames didn't hit fastballs in 2023. He was 25 runs above average against fastballs in 2021. That figure fell to 8 in 2022, but that's still sturdy. This past season, Adames was six runs below average on heaters. That problem wasn't confined to his slumpy May and June, either. It lasted throughout the season.

Ok, we've diagnosed a problem here. Adames didn't hit heat in 2023. That's just going by results, though. Using expected stats, including whiff rate and quality of contact, we can home in on Adames's process against those pitches. The picture looks rosier that way.

These are plotted out by month to dissuade anyone from thinking his problems were exclusive to that troublesome stretch in spring and early summer. Don't read into the apparent trendlines. The headline is that while Adames produced horrendous results against the fastball, the underlying metrics indicate that he was better than those results imply.

Alas, we can't quite stop there. There are times when expected stats and batted-ball data tell a clear and simple story, even (or especially) if that story belies the one apparently told by surface-level numbers. Just as often, though, they tell a complicated and self-contradictory tale. This is one of those times. For one thing, Adames's Barrel Rate on fastballs was up, but his average exit velocity was a full 1.5 miles per hour lower. His contact rate on fastballs in the zone was higher, but so was the rate at which he chased (and missed) heaters outside the zone. 

Here's the intriguing and encouraging news: the problem might be partially demographic. Here's a chart tracking expected weighted on-base average (xwOBA) against fastballs by age bracket, since the start of the Statcast era in 2015.

We can debate whether there's really much signal within the obvious noise, but the data says hitters have the toughest time hitting hard stuff from ages 25-27, and (perhaps peculiarly) the most success from ages 28-30. It seems improbable that a switch would flip between ages 27 and 28, of course, but talk to baseball people, and they can articulate a theory of the case. You have to learn how to find and zero in on your pitch, and that takes time. After 30, naturally, you're likely to decline, as catching up with pure velocity gets harder. The sweet spot, then, comes in your late 20s.

Adames turned 28 on Sept. 2. It's just possible that, as he continues to mature at the plate, he'll get back to mashing fastballs in 2024. That should inform our understanding of the Brewers' overall offensive outlook, and of Adames's future--two things that are, obviously, intertwined with one another, especially since this is the offseason in which the team needs to make their decision about whether to extend Adames and retain him beyond 2024.

Before committing to him (or not), the team needs to ascertain their level of confidence that Adames will take that step, because they have to hit fastballs better in 2024 than they did in 2023. They were 25th in run value against heaters this year. Christian Yelich, Sal Frelick and William Contreras (perhaps not coincidentally, the team's only three markedly above-average hitters) were the only guys who had strongly positive run values on those pitches. Adames was 280th of 330 qualifying hitters in fastball run value. Brice Turang was 328th on that list.

We already knew this, but the Brewers have to go out and add prime-aged hitters with power to their lineup this winter. That they specifically need to do better against fastballs only underscores that. Adames should be better on heat next season, between his age and some regression, but they need a lot more than a bit of friendly mathematical course correction.