BUFFALO — Gerrit Cole would rather not talk about what he puts on a baseball when he pitches.

Brian “Bubba” Harkins has no such issue.

As MLB’s crackdown on pitchers using foreign substances approaches and offensive numbers have already ticked up, the former Los Angeles Angels visiting clubhouse manager who was fired in 2020 for providing pitchers with a substance he made, told Sports Illustrated that some of the biggest names in baseball used his product.

Including Cole and fellow Yankee Corey Kluber, who Harkins said used the substance while with Cleveland.

A text allegedly from Cole sent in 2019 while he was with the Astros was included in Harkins’ defamation lawsuit against the Angels that has since been dismissed and is being appealed.

It read, “Hey Bubba, it’s Gerrit Cole, I was wondering if you could help me out with this sticky situation. We don’t see you until May, but we have some road games in April that are in cold weather places. The stuff I had last year seizes up when it gets cold.”

That led to an exchange in which Cole and Harkins discussed the mixture and Harkins allegedly sent Cole a custom-made batch, to which Cole responded: “Thanks Bubba you [the] man.”

Cole has repeatedly declined to address the issue and was unable or unwilling to answer a question about whether he’d ever used Spider Tack when he was asked last week following thinly veiled accusations from the Twins’ Josh Donaldson.

Donaldson pointed out that Cole’s spin rate had dropped after a report came out that four minor leaguers had been suspended this season for using foreign substances.

Spider Tack, as well as Harkins’ formula — which he told SI was a mixture of liquid pine tar, solid pine tar and rosin — are among the substances pitchers have used to improve their command.

What hitters — and now MLB — have grown concerned about is the increase of usage and advanced technology have taken it from pitchers getting better control to being able to throw “nasty” pitches, as Donaldson put it.

Harkins told SI that he shipped tins of the “sticky stuff” to pitchers like Cole and Washington’s Max Scherzer, as well as Kluber.

The former Angels clubhouse staffer told SI he learned how to make the substance in the mid-1990s from Troy Percival. Percival, who declined comment, also made it in Detroit, where he introduced it to former Yankee Joba Chamberlain.

It was Chamberlain, then, who made Kluber aware of it, according to Harkins.

Kluber’s agent, B.B. Abbott, refuted Harkins’ claims that Kluber used the substance in a statement to SI, saying “[Harkins] never personally gave anything of the sort to Corey Kluber nor has he ever used any substance prepared by Bubba [Harkins] in a MLB game. If he is saying anything contrary to that, it is a blatant lie.”

MLB has rarely disciplined pitchers for using illegal substances. Michael Pineda, while pitching for the Yankees in 2014, was suspended for using pine tar after the Red Sox could see it on his neck. A year later, Will Smith of Milwaukee and Baltimore’s Brian Matusz were both forced to sit eight games.

Earlier this month, major league owners met and agreed to increase enforcement of the rules, with strikeouts soaring and offense plummeting.

Umpires are expected to be able to check pitchers’ uniforms, caps and gloves for illegal substances.

On May 27, umpire Joe West confiscated the hat of Cardinals reliever Giovanny Gallegos for appearing to have a substance on his brim.

As the wait for the real crackdown continues, the rules’ enforcement has been praised by many players, at least publicly, with Giancarlo Stanton and even pitchers Zack Britton and Jameson Taillon coming out in favor of it in hopes of leveling the playing field.