When Danny Duffy first arrived in the big leagues, he was electric. As a guy, he’s naturally laid back — perhaps a product of having grown up in southern California — but he used to throw really hard. Unfortunately, the velocity didn’t necessarily translate to success. Duffy lacked real command of his repertoire. As the left-hander put it to me recently, he “had no idea where the ball was going.” He threw mostly just four-seam fastballs and a curve.

Duffy has evolved pretty considerably since his rookie season in 2011. It’s not that he’s just a command guy now — he still throws hard — but a lot has changed over the last few years. With more than a month left in the season, Duffy has already recorded the highest WAR figure (2.9) of his career.

What happened? What allowed him to refine his command, to establish a more ideal pitch mix? Duffy recently helped answer those questions, relating all the “aha” moments that led to a completely different, and much more successful, arsenal — an arsenal I address pitch by pitch in what follows.

The Fastball

This year is the closest Duffy has ever come to throwing more sinkers than four-seamers. There’s always a ground-ball benefit — “I started getting more ground balls, more weak contact,” said Duffy, who is currently enjoying the highest ground-ball rate of his career — but this change was more about command than outcomes on balls in play.

When Duffy first came up, the refrain was that he’d go as far as his command would take him. “I thought I had to be so fine when I was younger, because I struggled with the strike zone so much,” Duffy remembered. “Then I figured out that it was all about repetition. You can’t expedite it; experience will give it to you.”

But that doesn’t mean that the switch to the sinker didn’t help him when it came to command. “You didn’t have to be so fine with it,” Duffy pointed out. Now he can throw the sinker to the middle of the plate and let the movement take it to the edges. “They literally tell me, ‘Start it over. Start it over,'” said Duffy. “I kinda backed away from front-dooring righties with it because I didn’t want to be so fine with it and leave it out over. I’d rather start it middle and let it finish on the outer third.”

During a period in a relief role, Duffy also learned another little trick. He gave up the windup and pitched exclusively out of the stretch, to simplify things — creating “fewer moving parts,” as the pitcher put it.

Duffy has recorded a 6% walk rate the last two years, on the back of a 63% first-pitch strike rate. His first two years in the zone, when he was hucking straight four-seamers? A 12% walk rate and 52% first-pitch strike rate, respectively.

The Breaking Ball

When he wasn’t throwing a fastball back in 2011 and 2012, Duffy was most likely throwing a curve. The thing had two inches of extra movement laterally and vertically, and went 2 mph faster than average, but it never got average results when it came to whiffs. That might have had to do with his trouble getting hitters into counts where they felt they had to swing. The numbers support that theory: Duffy never recorded even an average swing rate on the curve.

All that is prologue at this point. Because, since he came back from Tommy John surgery in 2012, he’s been afraid to throw what was once considered his best secondary pitch. “I had this mental block where I was afraid to expose my elbow like that,” Duffy said of throwing the curve after surgery.

Apparently his ligament blew on a curveball. “I was hurting the whole outing, but that was the pitch. That’s when it blew out, a curve to Adam Dunn.” The lefty realizes that it wasn’t the curve’s fault, but that doesn’t mean he loves throwing the pitch any more. “I’ve thrown like seven this year,” he said of bringing it back.

In its place? A rip-roaring slider, born of a little messing around. “So in the ALCS a couple years ago, me and Kris Medlen were playing catch, and we were messing around, and I said, ‘Dude I’m going to grip this four-seam and throw this like a football.’ And I did exactly that, and it was disgusting the first time I did it.”

This one gets three inches more depth than your average slider, and above-average whiffs for its effort. Disgusting:

The Changeup

This one is the most subtle. But if you graph the drop on his changeup against its usage, something pops out. He’s improved the drop on the pitch and has started using it more often.

Danny Duffy’s Changing Changeup Year Changeup Vert Changeup% 2012 2.85 10.5% 2013 2.56 17.8% 2014 2.44 9.0% 2015 2.53 10.1% 2016 3.82 17.1% 2017 3.45 22.1% SOURCE: Pitch Info Changeup Vert = difference between four-seam & changeup vertical movement (4.3 is average)

Again, Duffy learned from a teammate. “I saw Edinson Volquez on the super slow-mo, and I thought I would just grip the four-seam, and put my pinky on the equator, and not pronate really, and just rip through it,” Duffy said of the adjustment he made on the pitch.

It’s fairly difficult to see, because it was such a small change. He modeled his old grip (left) on the new (right), but you might be able to notice that the seams are different and his pinky is tighter on the ball these days.

Since he isn’t thinking about pronating the pitch to give it more movement, it follows that he’s throwing the pitch with more arm speed. That should add deception, as it looks like a fastball in terms of effort. And spin? “Now it has similar spin to my slider, so these guys swing right over it thinking it’s going to break in,” Duffy said.

The lefty gets a command benefit from the new changeup approach — “beauty of gripping it this way is that you’re not going to lose it, so now I can throw it to lefties, too,” he said — but the main thing is deception. Duffy’s best two best years for swing rates on the changeup have come in the last two seasons.

You could say that Danny Duffy broke into the big leagues as a guy with a good fastball and breaking ball combination, and that much would be true today. It’s just that it’s a different fastball, a different breaking ball, and a different approach on the change.

All these changes were fairly minor, but they added up to a pretty substantial difference. Now Duffy is one of the top starters in the league on a team duking it out for the postseason.

Of course, the work isn’t done yet. “It’s a process, I’ll probably going to have to change something again,” smiled the agreeable lefty.