(NewsNation Now) – Major League Baseball pitchers are throwing some serious shade on one of the sport’s new rules.

What is ‘sticky stuff’?

Sticky stuff, or goop, are two slang terms for foreign substances that pitchers use to enhance their grip on the ball. It can come in many forms — sunscreen, pine tar, or even specially engineered formulas that don’t have much conventional use outside the game. Pitchers can hide them on their hats, gloves or jerseys.

They’ve always been against the rules, but the league has looked the other way until now. The only approved substance is rosin, which can help dry the sweat off a pitcher’s hand.

Umpires have been instructed to check pitchers’ hats and jerseys for so-called “sticky stuff,” and managers can also ask them to check if they’re suspicious a pitcher might be using a banned substance. It’s lead to some theatrics so far.

What happened between Max Scherzer and the Phillies?

Tuesday night, the Washington Nationals’ Max Scherzer started against the Philadelphia Phillies. Umpires did their now-regular screenings at the end of the first and third innings. Scherzer, a three-time winner of the Cy Young award for the league’s best pitcher, seemed annoyed at the checks, but complied. The umpires didn’t find anything.

However, Phillies manager Joe Girardi noticed Scherzer was touching his hat and hair in the fourth inning and asked the umpires to check again. This time, Scherzer was so off-put that he started removing his belt like he was in an airport security line and encouraged the umpires to touch his sweaty hair.

The umpires did touch his hair and, for a third time, didn’t find anything.

He said after the game he’d “be a fool” to use a banned substance on a night when he knew the umpires would be so focused on it.

But Girardi had upset the Nationals’ coaching staff, and after chirping back and forth from the dugout, he stepped onto the field to continue yelling. The umpires threw him out.

“He’s a con artist,” Nationals General Manager Mike Rizzo said of Girardi Tuesday morning on 106.7 The Fan in Washington, D.C. “He’s been doing that for years on TV.”

Phillies President Dave Dombrowski defended his manager.

“That’s not Joe Girardi,” he said. “It’s totally improper for (Rizzo) to say that. … Joe Girardi is the farthest from a con man of anybody that I know. He’s a very sincere individual. He was within his rights.”

Dombrowski added that he called Commissioner Rob Manfred’s office and MLB had already consulted with the umpires and determined Girardi’s request was legitimate.

“I love Joe Girardi,” Rizzo also said in his radio interview. “I’ve seen him play since he was in high school at Peoria, Illinois, scouted him at Northwestern. I know him well. But, I know him well.”

The Nationals won the game 3-2.

What did Sergio Romo do with umpires between innings?

Oakland A’s pitcher Sergio Romo came in for an inning of relief against the Texas Rangers later Tuesday night and took Scherzer’s antics a step further.

Between innings, an umpire asked to check him for foreign substances. Romo immediately undid his belt and slid his pants down a few inches. They never hit the ground, but the moment went viral in clips and GIFs online.

The A’s beat the Rangers 13-6.

Why is Major League Baseball checking for sticky stuff?

Offense is down in the sport, and conventional thinking among fans and insiders is the pitchers are much better than the hitters. This season, teams are averaging 4.41 runs per game. It’s down for the third straight year, and the lowest since 2015.

Pitchers, like Scherzer, have said MLB should provide a list of approved products instead of banning all substances. The pitchers say they use the substances to enhance their grip and give them better control as they pitch.

Hitters are split on the issue. Some say they don’t mind pitchers getting extra help since some of them are now throwing up to 100 mph, and the hitters would rather the pitcher know where that missile is going.

However, some say the substances help too much, and give the ball unnatural spin that’s hard for a batter to hit.

MLB is technically only enforcing the rules they currently have on the books. In order to make them more nuanced, as Scherzer’s suggested, the MLB Players Union would need to sign off on it. This change in enforcement was Commissioner Rob Manfred’s call.

The Associated Press contributed to this report.