Cubs right-hander Jameson Taillon wrapped up catch play and drills Monday afternoon, then wandered into the bullpen at Citizens Bank Park to watch fellow righty Ben Brown’s side session.

Brown locked in his bread-and-butter pitches — his fastball and curveball — first, then worked on the changeup, his newest pitch.

“The cool part is, I get to sit on the bench [Monday] night and go over it with Ben a little bit, talk about what he liked and didn’t like,” Taillon said in a conversation with the Sun-Times this week. “That’s where the value is at.”

Taillon and Brown had a breakthrough this year with the same pitch, a kick change.

For Brown, 25, developing a third pitch was key to establishing himself as a major-league starter in what has been an up-and-down season. For the veteran Taillon, it has been instrumental in helping him navigate the heavily left-handed lineups that opponents often roll out against him based on his splits.

“If you’re gonna get that opposite side out, there’s not too many guys in the game that don’t do it without a changeup,” manager Craig Counsell said before the Cubs’ 3-2 victory Thursday against the Pirates. “There are outliers, and some guys that don’t, but most do it with a changeup. And so it’s an important thing to have in your arsenal.”

Finding a changeup that works for Taillon, however, has been a yearslong process.

Tinkering with a new changeup in spring training is so common for pitchers that it has become a cliche. It’s difficult to know what’s actually going to stick until pitchers are further into their buildups and close to throwing at their usual velocity.

This spring was unique for Taillon.

He used his experimentation with Blue Jays right-hander Kevin Gausman’s split-change as a counter-example.

The first time Taillon tried out Gausman’s grip in a bullpen, the metrics jumped off the page: an elite combination of 16 inches of horizontal break and zero vertical. He threw it again, and the result was “awful.” It went past the catcher to the backstop.

“That’s the difference with this one: I never had quite as much fluctuation with it,” Taillon said. “It was a little more consistent vs. if I pursued [Gausman’s] grip longer, maybe I would figure out how to throw it for a strike more consistently. Or I’d hit the point I always do every spring, and I just bang it and never throw it again, and then I don’t have a changeup.”

The kick-change grip is essentially a relaxed circle-change grip, with the middle finger spiked. The ring finger and middle finger exert even pressure.

“It kicks the axis of the ball and lets the seam shift-drive it the other way,” pitching coach Tommy Hottovy said. “It’s physics, and it’s weird . . . but it works.”

Taillon and Brown differ slightly in where they place their middle finger, but it’s the same concept.

“There’s a level of comfortability there,” Taillon said, noting that he essentially just spikes his old changeup grip. “If I really wanted to optimize it even more, I probably could have done a different grip and optimize the metrics a little better. But I think this is the perfect mix of, plays into my arsenal really well, comes out of the same slot as my fastball. I’m not trying to pronate it or turn it over. So even when the metrics aren’t as good, it’s still coming out of my fastball slot 10 miles an hour slower.”

This season, Taillon’s changeup has overtaken his cutter as his third-most used pitch to left-handed hitters. Entering his start against the Pirates on Thursday, Taillon was throwing it at a 19.3% clip against lefties, according to Statcast. And it was generating an impressive 37.5% whiff rate.

En route to limiting the Pirates to two runs in 6„ innings, Taillon threw 15 changeups, getting four called strikes and two whiffs on four swings.

It has been working so well against lefties that Taillon said he’d at least like to put it in right-handed hitters’ heads, even if it doesn’t become a regular weapon against them.

Hottovy said before Brown’s last start that he expected a similar next step.

When Brown had his best two-game stretch of the season — against the Reds and Tigers the last couple of weeks — he had ramped up his changeup usage, to 6.5% of his total pitches and 9.8%, respectively.

On Wednesday in Philadelphia, however, he struggled with all-around command and allowed six runs in 5⅔ innings.

“The changeup was not the best it’s been,” Brown said of his last start. “But I threw some good ones. I threw some right-on-right, threw some for strikes, but there were just a couple of uncompetitive ones, which I haven’t really had so much [before].

“I think to righties, it’s reasonable to think that could be in my next outing.”

Brown’s changeup just below the strike zone to Trea Turner on Wednesday was the third changeup he had thrown to a right-handed batter this season.

Brown didn’t adopt the kick-change grip until midseason, abandoning the version he had honed in spring for something he could grip and rip. It has been helpful to watch Taillon’s pitch-development process.

“I watch [all] his bullpens,” Brown said. “You see the consistency, you see what it looks like in games, that he trusts it. It’s [so] encouraging.”