So much pitch development happens these days in close coordination with Rapsodo data and high-speed video that helps every pitcher carefully hone his spin axis, spin rate and release mechanics to fit his arsenal. There’s much more understood about when to throw those pitches and how to sequence them, too.

And then, there’s Tyler Duffey, who has started to mess around with a slow curveball this spring, more or less because it “looks so weird.”

Duffey has relied on a knuckle curveball throughout his career, but nothing quite like this — a change-of-pace offering that floats up out of his hand and drops like a stone. It got down to 68 mph earlier this spring when he slipped on his delivery. He’s not even quite sure what to call this thing.

“I talked to [advance scout Colby] Suggs a lot about it,” Duffey said. “I keep calling it my changeup, just because … I don’t have one. It was never really good when I did throw it. Call that my changeup for now, and we’ll see what happens.”

Considering he’s been one of the most effective relievers in baseball across the better part of the past two seasons, Duffey has the wiggle room to experiment like that — especially after his regular stuff worked as well as it did on Tuesday against the Pirates. Duffey threw nine curveballs in the eighth inning. Pittsburgh batters swung at six of them — and missed all six times. He struck out a pair in a clean inning.

That kind of dominant outing certainly helped Duffey put behind a tough start to Spring Training during which his fastball velocity had been down. On Tuesday, that was back up to an average of 92.6 mph, and he said all of his pitches immediately felt much better out of his hand.

The key has been some mechanical cleanup Duffey has been doing on the back fields, which hadn’t been translating to the mound in his first four appearances of the spring.

“Duff is spending some time working on some things on the back fields and he’s using this Spring Training as a growth period in a few ways,” manager Rocco Baldelli said. “Some of them may be mechanical, some of them may be routine-based, but he’s using his time very well, and he threw the ball awesome.”

Duffey is just as excited about the slow as he is about the fast. He mixed in two of those “changeups” on Tuesday, which floated to the plate at 71.5 mph (foul bunt) and 69.5 mph (ball). He’s trying to have a little fun with it, considering it’s Spring Training and he has the chance to throw it more often than he would during the season. He doesn’t think it’s going to be a weapon, per se, but he likes it as an occasional change-of-pace option to change hitters’ eye levels.

The idea originated in 2018, when Duffey shared a Triple-A dugout with curveball whisperer Ryne Harper and saw that hitters just couldn’t wait for it. The first time Duffey threw it to a hitter was to Eddie Rosario in Summer Camp last year — and Rosario nearly swung out of his shoes.

“Everything is so geared for velo now,” Duffey said. “It’s hard for them to slow that down. I was like, ‘I want to see if I can do it.’ So I tried here or there, and now I’ve gotten to where I’m really, really trying to slow it down.”

Kind of like Zack Greinke, who sometimes makes a sport out of that?

“Yeah, exactly,” Duffey said. “It’s just so slow, it’s like you don’t want to swing at it, because it’s going to take you out of your game. Ultimately, if you can keep it over the plate, it can end up being a useful pitch. And it’s fun.”

Duffey has gotten the reactions that he’s wanted to see from it this spring — and he hopes to expand that to some more right-handed hitters, who could see it differently due to Duffey’s release point. He’s just got to pick and choose his moments.

Say, not when Nelson Cruz is at the plate in live batting practice.

“I don’t know if I’d feel comfortable telling him, unless I had an L screen in front of me, maybe, then I’d lob one up there,” Duffey said. “He’s one of the ones I was concerned with.”

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