Tonje was on his initial move to the right. Mag slipped his right arm between Tonje's body and free arm effectively blocking him from hooking Mag with that arm like he had all game. It's just a split second, but it's clear it's the piece that prevents Tonje from getting a step and working around Mag for the easier basket and potential AND-1.

Mag blocked the hook, and it completely changed the play.

https://twitter.com/TorresOnBYU/status/1903697692884337128