San Francisco Giants first base coach Antoan Richardson claims he was ejected on Tuesday night for confronting a Padres coach over what he says was a comment that "reeked" of racism.

Richardson, who's Black, made the allegations following SF's win over San Diego ... saying it all started in the third inning, when Padres coach Mike Shildt, who's white, picked a fight with him while he was in the Giants' dugout.

Richardson told media members that Shildt was looking for someone in the Giants' dugout ... and when he asked who he wanted, Shildt got snippy.

"At this time, he's walking toward our dugout," Richardson said of Shildt. "And then he says, 'Hey. I was looking for Alex Wood.'"

Richardson says the exchange of words got so heated, SF manager Gabe Kapler came over to defuse the situation. Then, that's when he claims Shildt unleashed a comment that he believed dripped with "undertones of racism."

"He yelled, 'You need to control that motherf***er,'" Richardson said.

Richardson said he was so taken aback by the comment, he stepped toward the top of the dugout to confront Shildt -- and was ultimately ejected for the action.

"His words were disproportionality unwarranted," Richardson said of Shildt. "And reeked of undertones of racism. When he referred to me as 'that motherf***er,' as if I am to be controlled or I'm a piece of property or enslaved."

Richardson then ripped MLB umpire Greg Gibson for ejecting him ... saying, "Me being tossed by that umpire empowered this coach to continue to have conversations like that with people like me. And that's really unfortunate that that's what happened tonight."

Shildt -- who managed the St. Louis Cardinals last year -- and Padres manager Bob Melvin did not comment on the incident following the game.

While it was all a disturbing situation for Richardson, his ejection did lead to some MLB history -- Alyssa Nakken took over his coaching duties on the field ... and became the first woman in MLB history to ever do so.

"I'm really excited that Alyssa (Nakken) got her opportunity to make her Major League debut and I'm very proud of her," Richardson said. "I think she did a really wonderful job and we got a win, so that's the most important thing."

Kapler, meanwhile, addressed the incident following the game and said he believes Richardson's side of the story to be true.

"I trust Antoan's judgment 100 percent. I trust Antoan's judgment on the matter and I know that Antoan was not out of control at all and that anything that was said to insinuate that he was is totally inappropriate."

"He didn't instigate any part of this."