The Boston Celtics are navigating one of the most eventful offseasons in recent memory. The Jaylen Brown trade has dominated the conversation, and the roster is taking shape around a healthy Jayson Tatum heading into the new season. Head coach Joe Mazzulla, meanwhile, has been doing what he always does in the offseason.
Training. Hard.
Footage shared by MMA insider Ariel Helwani captured Mazzulla working through intense pad drills and grappling sessions at the renowned Xtreme Couture gym in Las Vegas, training under acclaimed MMA coach Eric Nicksick. The clips traveled quickly, and for good reason.
What Was Captured
The footage showed Mazzulla fully committed to his combat sports routine, looking every bit as focused in the gym as he is on an NBA sideline. It was not a casual workout. It was the kind of session that reflects genuine dedication to a craft he has been developing for nearly five years.
Mazzulla has made MMA and Brazilian jiu-jitsu a regular part of his life, often visiting local gyms during Celtics road trips to maintain his routine throughout the season. The offseason simply gives him more time to dive deeper into it.
Why He Does It
The training is not just about physical fitness. Mazzulla has frequently drawn parallels between the mental demands of combat sports and the requirements of coaching an NBA team. Discipline and composure under pressure are qualities he has credited his MMA training with helping to sharpen.
His ongoing relationship with Nicksick goes beyond physical preparation. The two regularly exchange ideas about building championship habits. It reflects how seriously Mazzulla takes every dimension of his development as a coach.
The Celtics Coach Behind the Training
Joe Mazzulla, Boston Celtics
Mazzulla’s coaching career has been one of the fastest rise stories in recent NBA history. He joined the Celtics as an assistant in 2019, became interim head coach in 2022, and guided Boston to the 2024 NBA championship, becoming the youngest coach to win a title since 1970.
He followed that with the 2026 NBA Coach of the Year award after steering the Celtics to the second seed in the East despite Tatum missing most of the season with his Achilles injury. Including the playoffs, Mazzulla owns a 274-111 career record, the highest winning percentage among coaches with at least 200 games on an NBA sideline.
Final Word for the Celtics
Joe Mazzulla spends his offseason training in MMA gyms. It is entirely on brand for one of the most unique personalities in professional basketball.
The Celtics are entering a new era without Brown. Whatever comes next, their coach is putting in the work to be ready for it.
Celtics’ Joe Mazzulla Goes Viral in Stunning MMA Footage