Merrill Kelly stepped off the rubber and glared right at Cubs third base coach Quintin Berry, making it quite clear that he had beef with him.

It’s one thing if a player steals signs during the course of game.

It’s another when a coach, like Berry, is believed to be doing so.

“Stealing signs is as old as baseball. I think it’s a little bulls–t when it comes from a coach,” Kelly said Monday night after suffering the loss in the Diamondbacks’ 7-0 home loss to the Chicago.

“If it’s a guy on second base and they see a grip in your glove or if the hitters can see something you’re doing with your glove, I think that’s fair game. I think guys have been doing that since the beginning of baseball. I think it’s a little bush league when it comes from outside that. I think inside the lines is one thing, I think the guys that are standing outside the lines I think it’s a little bush league.”

Things got heated in the desert Monday night with both benches yelling at one another mid-game and Kelly later calling out Berry for allegedly stealing signs at Chase Field.

Stealing signs is part of baseball culture, with the onus falling on the pitcher and the catcher to ensure that men on second base cannot just relay signs easily.

Players will get agitated when that happens, but there’s an understanding.

Sign stealing from coaches is viewed differently, although there are no technical rules against it.

Kelly, who allowed three run in 5 2/3 innings, believed that Berry “had something” on his changeup that allowed him to tip off the Cubs hitters, especially lefties.

The broadcast showed him stepping off to stare at Berry while pitching to lefty Michael Busch in the fifth inning while trailing 2-0.

“That was probably the most egregious I’ve seen from coaches,” Kelly said of the alleged sign stealing. “Everyone in this game is trying to get an edge wherever they can. Definitely not the first time a coach has relayed signs, but I think tin that situation I think it should stay between the players.”

While Kelly kept his relative cool, Arizona’s staff did not.

Diamondbacks pitching coach Brian Kaplan supposedly yelled at home plate umpire Lance Barrett, per the local broadcast, while also motioning toward Berry.

Diamondbacks bench coach Brian Bannister appeared to yell toward the Cubs’ bench, pointing his finger and later wagged it in a “don’t do that” manner.

Cubs bench coach Ryan Flaherty at some point pointed back and seemingly said: “F–k you.”

Berry didn’t seem to be bothered, turning toward the Diamondbacks dugout with a smile and seemingly saying: “All f–king day.”

Cubs manager Craig Counsell downplayed the situation.

“That’s gamesmanship that goes on every day in the league,” he said.

Amid all the bickering, the Cubs picked up an important win to push their lead for the top NL Wild Card spot to three games.

Arizona, meanwhile, is now two games behind San Diego for the final spot.

While Kelly did not love the Cubs’ tactics, he noted that he did something wrong if they could pick up a tell that easily.

“That being said, I got to take a look at what I’m doing because clearly he had something and obviously if he has it then other people will probably pick up on it as well,” Kelly said. “I gotta figure out and do better on my part to not give it away. Yeah, I think it should stay between the players.”