American tennis sensation Coco Gauff had to tell her father to keep cool as he was coaching her on the sideline of her Auckland Open match against Laura Siegemund on Thursday.

Corey Gauff was mic’d up when he was talking to his 15-year-old daughter during her match. Corey Gauff appeared to slip and say “damn” while he was delivering a pep talk.

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“There's one thing you did the last three games, you ain't give up no free points on no damn serve. That serve is weak,” he said.

Coco Gauff told her father to pump the brakes with his language, saying “you can’t curse.” He later apologized but didn’t believe he actually cursed when his daughter reminded him that he said the “D-word.”

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“Oh, well that don't even count,” Corey Gauff responded.

Coco Gauff won the opening set against Siegemund 7-5 but dropped the next two 6-2, 6-3 and lost the Round of 16 match, putting a potential game against Serena Williams on hold.

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Coco Gauff burst onto the scene last summer at Wimbledon when she became the youngest player in a match at the event since 1991. She played in the U.S. Open later in the Grand Slam season but lost in the first round to Naomi Osaka.