LAS VEGAS — Cooper Flagg made his professional debut Thursday night in the NBA Summer League and celebrated an 87-85 win over Bronny James and the Lakers.

Flagg finished with 10 points on 5-for-21 shooting, including 0 for 5 from 3-point range. He also had six rebounds, four assists, three steals and one block. Though Flagg struggled at times to find his groove, there were flashes as to why he was chosen No. 1 overall last month, doing plenty of little things that helped the Mavericks seal the win, including a key block near the end of the game.

Flagg swatted DJ Steward’s attempt with 1:10 left in the game, and Ryan Nembhard made a 3-pointer at the other end to give Dallas the 87-85 lead.

“I couldn’t really get into a rhythm, it’s a different environment, obviously very different from college, it’s probably very different from what the real NBA is gonna be like,” Flagg said after the game. “The coaches had a lot of confidence in me. They’ve been telling me they want me to experiment, try some new things, and I was trying to be aggressive, and that’s new for me too.

“I would say that might be one of the worst games in my life, but we got the win, that’s what really matters to me.”

Flagg strolled into UNLV’s Thomas and Mack Center at 4:17 p.m. on Thursday, wearing Dallas Mavericks gear, bright white New Balance shoes, and an emotionless look on his face as he passed through security.

Roughly 45 minutes later, he wore the same stone-cold face as he came out for warmups shortly after 5 p.m.

“I was obviously a little nervous, it’s a new environment, a lot of new fans and whatnot,” Flagg said. “So I was a little nervous, a little excited, but just happy to be here. It’s a dream come true, so I’m just trying to enjoy the moment.”

His fans more than made up for it with plenty of energy, electrifying the jam-packed arena that cheered loudest when he was announced as a starter in his first Summer League game.

Flagg missed his first two attempts of the game, picked up his first foul just 46 seconds into the game, and gave the crowd what they’d been anticipating, going one-on-one with fellow fan favorite James.

Generally filled with Lakers fans when the team plays in the summer, the arena was full of emotion with a fair share of Mavericks fans in attendance to see the 2025 National college player of the year.