In just the last decade, we’ve seen a major shift in how starting pitchers behave, how they’re used, and how they attack hitters. For so long the fastball was far and away the dominant pitch in any arsenal, but we’re approaching a point where it will merely be a plurality of pitches thrown by starters, no longer a raw majority.
This past year saw the lowest rate of fastballs thrown by starters in at least the last decade:
MLB starting pitcher usage rates
Carlos Carrasco has seen much the same change in his nine year career. This past year we saw Carrasco — he of the 94.1 mph average fastball with good life — throw a career low in four-seam fastballs:
Carlos Carrasco career usage rates
It resulted in his highest strikeout rate in three years, a career low walk rate, and his second highest single-season WAR total. It also resulted in Carrasco’s highest Hard Hit Rate (batted balls over 95 mph) in his entire career by a considerable margin — the 38.9 percent mark he set was 2.5 points above his former high, 36.4 in 2016, and 14 points higher than his career low in 2014. This is a bad sign, giving up more hard hit balls as you age, and it needs adjustment.
Before last season I thought what would work for Carrasco was featuring his slider more than in years past. It had long rated as a strong pitch, by FanGraphs’ Pitch Values its career 47.9 Pitching Runs is his highest mark, and was topped in 2017 by only his changeup, 12.5 versus 18.3. If he was going to reduce his fastball output, It would stand to reason that the slider - so much like the the fastball in velocity and movement, right up until the end — would be the pitch to take up the slack.
It worked, at least for the most part. Carrasco was great. But that spike in Hard Hit Rate is troubling, something that appears like a canary in the coal mine warning for an aging pitcher. He still has above average velocity on the fastball, but with the specter of age ever looming, I fully expect that average velo to slip below 94, narrowing his margin for error. The slider will be vital to that, but what about that changeup? Is this the year that it takes its place as a primary secondary pitch?
He was successful with it in 2018, hitters were only able to put it in play 15.4 percent of the time. That’s just the 31st best mark on that pitch among starters, but does rank above Trevor Bauer (16 percent) or Max Scherzer (16.4 percent), two guys with elite changeups in their own right. He also got a swinging strike on it 24.4 percent of the time, which ranked 6th in baseball. It’s been a great tool for him in the past, if his velocity does start to diminish it would behoove him to feature it a bit more.
Carrasco’s featuring of the slider to the degree he did in 2018 was a decided departure from the type of pitcher he’d been for so long. Prior to last year he’d never thrown anything besides the fastball more than 20 percent of the time. It was his unique strength in an elite rotation — unlike Kluber and his slurve, Bauer and his curve, or Salazar and his velo/change combo, Carrasco was a Jack of All Trades. He got away from that a bit in 2018, and admittedly had a great year. He’s got to stay ahead of the game though, and folding some of his other pitches back into the mix, especially as the fastball continues to fade bit by bit, will be vital for 2019 and beyond.