MLB's Ketel Marte Breaks Down In Tears Over Heckler's Taunt About Late Mom

9:23 AM PT -- The Chicago White Sox told ESPN a 22-year-old fan has been indefinitely banned from Rate Field over the incident.

A heckler crossed the line during the Diamondbacks game Tuesday night -- making a comment to Ketel Marte that was so insensitive, it actually reduced the baseball star to tears.

The emotional scene unfolded late in Arizona's tilt vs. the White Sox ... after a fan had made a remark to Marte around the time he popped out to end the top half of the seventh inning.

The Snakes' second baseman was seen on the game's broadcast being consoled by his teammates and coaches in the middle of Rate Field's infield ... and, initially, nobody had any clue why he was sobbing.

Minutes later, though, it was revealed a Sox fan had yelled about Marte's mother, who tragically passed away in a 2017 car accident.

Marte needed several moments to collect himself ... but he was eventually able to finish off AZ's 4-1 victory. Afterward, D-Backs shortstop Geraldo Perdomo was furious over the matter -- and called for the heckler to be banned.

"That can't happen," the Diamondbacks star said. "We can't continue to do that s*** here in MLB."

Marte did not address reporters after the game. His manager, Torey Lovullo, did ... and was clearly bothered by the incident.