Cooper Flagg's Trainer Details the Work Behind the Mavs Star's Next Leap

Cooper Flagg’s rookie season was already one of the best in recent memory. His trainer believes the best is still ahead.

Matt Mackenzie, who works with Flagg on his skill development, appeared on the Jimmy C Hoops podcast and detailed what the reigning Rookie of the Year has been focused on this offseason. The work, he said, is deliberate and targeted at the exact areas that separate elite rookies from true superstars.

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The first priority is durability.

“Really just making sure his body is durable to withstand 82 games plus playoffs,” Mackenzie said. “The transformation that he’s making to his body has been remarkable.”

Flagg missed eight games with a foot injury and later sprained his ankle in the final game of the season. Strength and conditioning work has been central to his summer, with the goal of holding up over a full NBA schedule and postseason run.

On the court, the focus starts with shooting. Flagg hit around 34% from three as a rookie on high volume while carrying a heavy offensive load. Mackenzie is pushing him to expand that range and consistency.

“Turning some of those long twos into threes, really working on attacking that three-point line and becoming comfortable shooting that three off the dribble and off the catch,” he said.

He also cautioned against overreacting to rookie efficiency numbers.

“Traditionally, he continues to trend up as you go into Year 2, Year 3. And I have no doubt that Cooper will do that,” Mackenzie said.

Beyond shooting, Flagg is refining his finishing package, improving his ability to absorb contact and sharpening his decision-making in live reads. His training mixes individual skill work with small-sided games that force him to read defenses, find cutters and operate in different actions.

“He has shown a ton of growth this summer,” Mackenzie said.

That growth builds on a historic rookie year. Flagg averaged 21.0 points, 6.7 rebounds, 4.5 assists and 1.2 steals while leading Dallas in all four categories. He became the first rookie since Michael Jordan to do so and the first teenager ever to score 50 in a game.

The blueprint for his leap resembles Luka Doncic’s second season, when improved shooting and tighter decision-making turned him into an MVP candidate. Flagg already has elite passing vision, defensive versatility and size. If the jumper improves and the finishing sharpens, superstardom is within reach.

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The difference is context. Doncic had to carry everything and Flagg does not.

With Kyrie Irving returning from injury, Dallas can ease Flagg’s burden. Instead of being the sole engine, he can play alongside a proven All-NBA guard who handles late-game creation and defensive pressure.

That changes everything. Flagg can grow into his role rather than be forced to define it overnight. Doncic had to be great because he had no choice, Flagg gets to be great with help.