Danny Duffy’s Innings, and Looking for Fatigue


Mandatory Credit: Peter G. Aiken-USA TODAY Sports

For most of his start on Sunday afternoon, Danny Duffy was cruising. After 6 innings, he had allowed just 1 run on 2 hits, both of which came in the 2nd inning. Despite struggling in the 7th before being replaced, Duffy had yet another solid start for the Royals. He pitched 6.2 innings, and the fourth run charged to Duffy only scored after a pair of singles allowed by Jason Frasor. Obviously you’d like to see better strikeout and walk numbers (4 and 3, respectively) but he continued the trend of allowing weak contact in front of elite defensive players.

That method definitely seems to be working for Duffy, who now has an ERA- of 66, which ranks 6th in the league among pitchers with at least 100 innings. In the last calendar year, Duffy’s been even better, producing an ERA- of 57, trailing only Johnny Cueto and some guy named Clayton Kershaw in all of baseball.

While he has been great at preventing runs, and proven himself to be a key part of the team’s resurgence, the Royals also may be keeping an eye on his innings in his first full season after Tommy John surgery. As David wrote the other day, the team certainly has some options to limit Duffy’s workload, and it definitely makes sense to try and keep Duffy as healthy as possible, considering his long-term value to the organization. We all know about the theory behind limiting a pitcher’s innings after surgery, but I wanted to see if Duffy has started showing any signs of fatigue as he inches closer to a career high in innings pitched.

Looking at his velocity, Duffy seems to be staying pretty steady, for the most part. Outside of a couple of starts, most of his games have shown him to average roughly 94 MPH on his fastball. Unfortunately, one of those starts wasn’t that long ago, against the Twins, but he’s bounced back nicely from that night.

There does appear to be a slight downward trend overall, though, slight as it may be. I’m not going to say I’m concerned, but it is something to monitor in the next couple of weeks. If it continues to slide down, that could be a sign that Duffy is nearing his limit. Plus, Duffy’s fastball is his best pitch, and his most-used pitch, so any lost velocity could affect its effectiveness. As of right now, Duffy has arguably the most valuable fastball in baseball, so it would be nice if he can maintain what he’s done so far.

The other thing I wanted to look at was Duffy’s release point, because pitchers may start to drop their arm down a bit as they wear down, so a downward trend could signal fatigue. Luckily, it doesn’t look like much has changed for Duffy there, since his move to the rotation. This is true for both his horizontal and vertical release points, so hopefully that means Duffy isn’t dealing with any kind wear on his magical left arm.

If you’ll grant me a brief sidebar, I did want to point out one thing on the horizontal release point that caught my eye, though.

Following his start on June 14, it looks like Duffy made an adjustment that brought his release point in more. This can be done with an alteration to his mechanics, or by moving slightly to his right on the mound. It isn’t terribly drastic, but that release point has been much more consistent in his last 10 starts, so perhaps he and Dave Eiland found something he needed to correct. Since that start, Duffy’s thrown 61.2 innings with a 2.34 ERA, 7.15 K/9, and 3.21 BB/9. From what I’ve been told, those numbers are pretty good.

What I find even more interesting about this potential change is that it came after a start against the White Sox, in which Duffy pitched 7 innings of shutout ball, with 9 strikeouts and 1 walk. One would think a pitcher wouldn’t want to change anything following that kind of dominance, but maybe it’s something they had discussed previously. I’m not familiar with the inner workings of that relationship, but if this is something they wanted to work on, the move appears to have paid off.

This adjustment has drawn me away from my original point, so let’s finish that up.

Duffy is obviously hugely important to the Royals’ success this season. He’s also going to reach a career high in innings pitched within the next couple of weeks, and while there aren’t any very strong indicators that he’s already beginning to fatigue, the team will certainly want to keep a close eye on him to make sure he can maintain his effectiveness, for this year and several years to come.