When looking at his changeup usage over his career, we can see that Duffy keeps it strictly for right-handed batters, as each season he’s thrown at least 85% of them against righties. It doesn’t drop as much as other changeups around the league, falling bellow league average in vertical break by almost 4 inches, but this did not prevent it from being an effective pitch as it generated a very good whiff rate of 32%, an increase of 3% from last year. In addition, batters hit .231 against it with a wOBA of .300.
Duffy’s curveball usage hovered around the 20% mark in his first 6 seasons but drastically dropped to under 1% from 2015 to 2017. Duffy explained that he abandoned the pitch because it was the pitch that eventually blew out his elbow. However, over the past two seasons, he’s regained confidence in it and its usage climbed back up to the 9% mark. It has always been a very good pitch for him, generating an elite vertical break much above league average, which helps him get a good amount of whiffs with a rate of 25%. He’s thrown it 459 times since last year and has yet to give up a homerun.
Duffy’s fastball dropped 3 mph in the last three seasons from what it was in 2016. In that same time span, he’s seen the average exit velocity go the opposite direction and increase year after year, consequently seeing an increase in homerun count as well. This season, the pitch did generate a low batting average of .255 but gave up 21 extra base hits which is 6 more than last year.
Duffy used his slider almost twice as much against lefties than righties (65% vs 35%) and had good success with it garnering a whiff and strikeout rate of 31% and 23% respectively. As he’s slowly gaining confidence back in his curveball, it is possible that we see a drop on slider usage since it’s the pitch that replaced the curve.
Duffy’s four-seam fastball was his primary offering, although he didn’t have a lot of success with it. It’s been a fairly average pitch most of his career, and opponents batted .252 against it. Despite it being his most used pitch, he only managed to accumulate a 3.3 pVal. Even with increased arm-side run and drop, it remains an extremely average heater.
Duffy’s changeup usage remains in line with his career numbers, at his second-highest thrown of any of his pitches. He does get a fair amount of swinging strikes on it — although they haven’t translated to a good strikeout rate. It’s been another average offering in Duffy’s arsenal.
Duffy’s sinker dropped in usage and remains an average offering at best. Not many batters chased his two-seam fastball, and it resulted in a whopping 18.9% walk rate on the pitch. It was batted around for a .345 average despite its low HR/FB rate.
Duffy’s slider usage dropped concurrent to his increase in curveball use. While his slider was bad enough to dig a -10.2 pVal hole over the season, he did cut its usage by more than half. Clearly, the pitch was not working for him, and with the success of his curve, the slider’s limited role is more appropriate to his arsenal.
Duffy relied on his curveball as an out pitch, increasing its usage from next to nothing. Not only does he rarely walk batters on it, but it is also an above-average strikeout offering, which held opponents to a mere .049 ISO. Its increase of vertical drop has made him more effective in limiting extra-base hits.