It’s hard to imagine now, but one-year ago Zach Duke was not pitching in the major leagues. Duke was released by the Washington Nationals on June 10, 2013, after racking up an 8.71 ERA / 4.55 FIP over 20.2 IP. The Cincinnati Reds signed him a few days later then shipped him to their AAA affiliate in Louisville. In a recent interview with Andrew Gruman, Duke said:
“I figured out I needed to do something different to get a chance to be in the big leagues again… I really was going to try anything.”
Well, the changes Duke implemented worked. Not only is he back in the bigs, but Duke, and his 0.9 fWAR, has been the Brewers’ most valuable reliever so far this season. Yes, higher than Will Smith (0.7 fWAR) and K-Rod (0.5 fWAR).
So how sustainable is Zach Duke’s surge? First, let’s look at the big adjustment he made – lowering his arm slot. Duke’s new sidearm delivery is apparent thanks to the good folks at Brooks Baseball. Here are Duke’s release points from the 2007 season (earliest Pitch F/x info) until June 2, 2013, the last game he pitched for the Nationals.
Duke’s mechanical changes are evident but how good have the results been? To keep things simple, these are Duke’s splits during the corresponding dates above.
Obviously, Duke has a significantly smaller sample size throwing from the lower arm slot, but the metrics show promising improvement across the board. Statistically, things clicked once Duke adjusted his mechanics. Of course, the change in arm slot is a short-term advantage for Duke, especially with hitters who are familiar with him. The change benefits Duke in the initial sample size, but Duke didn’t just change his arm slot over the last year. No, Duke also added a new pitch.
As Gruman noted in his interview, Duke has adjusted his pitching arsenal. Gone is his change-up and, in its place, Duke has been dealing his slider more than ever – 27.1% versus his career norm of 6.7%. Prior to this season, Duke rarely threw his slider to right-handed hitters. That’s where he used the change-up. But Duke’s new, lower arm slot also changed the movement of his slider. Check out the spike in vertical movement on Duke’s slider once he lowered his arm slot.
Besides the new arm slot, now, hitters also have to deal with a better breaker in Duke’s arsenal. Duke’s new slider is a stronger pitch than the change-up he used to throw to RHH. In fact, all batters are hitting for a measly .111 AVG off Duke’s slider this year.
Of course, the Brewers couldn’t have expected this level of performance from Duke when they signed him to a $0.85M minor-league contract this off-season. For the Brewers, Duke has been a bet that’s paid out well, but there appears to be more value in his arm. The metrics suggest Duke has got the stuff to pitch in more high-leverage situations.
Currently, the Brewers bullpen has four southpaws, which is unusual but not crazy. It helps that Zack Duke has actually been better against RHH this year.
Of course, the million dollar question is how sustainable is this? How long before players adjust to Duke’s new arm slot and breaker?
According to Eno Sarris, one of his favorite indicators of potential, sustained success is K-BB%. Basically, it’s a good thing when pitchers can both miss bats and consistently find the strike zone. The Yankees Dellin Batances leads baseball with a 38.2% K-BB%. Zach Duke has a 29.5% K-BB%. That’s tied with Kenley Jansen for ninth best. Here’s how the Brewers’ qualified RP rank by K-BB%:
Zach Duke’s 11.5% SwStr% is also trending in the right direction. It’s almost five ticks higher than his career norm of 6.8%. If the control sticks, then so can Duke.
All together, it’s been quite the year for Zach Duke. At this point in 2013, Duke was sitting in Louisville. Telling himself that something needed to change. Well, something did. Don’t be surprised if Duke starts showing up in more high-leverage innings. He deserves them, and there are plenty of signs that he can, again, rise to that challenge.