Kelly Flagg reacts to son Cooper Flagg's electrifying poster dunk in Mavericks' win over Raptors

Cooper Flagg delivered a masterclass performance and led the Dallas Mavericks secure their first victory of the season. The former Duke star delivered a magical all-round performance, guiding Dallas to a 139-129 win against the Toronto Raptors on Sunday. Dallas rookie's mother, Kelly Flagg, was also amped after watching her son's magical performance at the American Airlines Center.

The No.1 pick had various highlight-reel plays during the game, none bigger than the first dunk of his career. With just over three minutes remaining in the third quarter, Flagg got a go-ahead pass from D'Angelo Russell in transition. The rookie went full steam toward the rim and rose high to paint a vicious poster on the Raptors' big man Sandro Mamukelashvili.

The crowd inside the arena went berserk and Flagg, who was fouled in the process, received a chest-bump from Anthony Davis. Flagg's mother, Kelly Flagg, gave a heartfelt two-word reaction soon after the video of her son's viral poster went viral on the internet.

"Yes ma’am!" she tweeted.

Cooper Flagg played 29 minutes on the night and was brilliant throughout the game. He finished with 22 points on 8 of 14 shooting, including 2 of 6 from beyond the arc. The rookie also tallied four rebounds, four assists and one block.

D'Angelo Russell praises Cooper Flagg

Cooper Flagg's electrifying dunk left not only the fans but even his Dallas Mavericks teammates in surprise. Anthony Davis' immediate reaction spoke volumes, while D'Angelo Russell praised the Mavericks' prodigy for controlling the tempo of the game.

"He’s unbelievable," Russell said of Flagg's dunk. "He does a little bit of everything, so when he’s getting the crowd going like that, our team feeds off of it. Everybody wants to see him do great, so when he’s performing like that it’s contagious."

The biggest positive for Dallas was Flagg's extraordinary outing on Sunday, which helped them snap their winless streak this season. It will be a quick change of favors for the Mavericks as Flagg and co. are set to face the defending champion OKC Thunder on the second night of a back-to-back on Monday.