Don’t do it.

Unfortunately for the Reds’ Freddy Galvis, he broke one of baseball’s “unwritten rules” and ticked off the Cardinals in the process.

The outfielder jogged across the front of the pitcher’s mound on his way back to the dugout. It happened after he flew out center field in the fourth inning of Cincinnati’s 4-3 loss in Game 1 of the teams’ doubleheader in St. Louis on Sunday.

The major no-no irritated Cardinals starter Miles Mikolas, who yelled his displeasure at Galvis. The incident caused the benches and bullpens to clear, though no punches were thrown. Galvis did not face Mikolas again because the right-hander was taken out after six innings.

“I asked him politely to use the grass,” Mikolas said after the game. “I asked nicely to not use that avenue again.”

Cardinals TV analyst Brad Thompson, who pitched for six seasons in the majors, said on the broadcast that what Galvis did is “frowned upon” and it’s “easy to go around” the mound.