My guess...
Per Abby Chin, Stevens told the starters that they've been outplayed the entire game and they have a few minutes to show him why he should keep them in. A couple of minutes later Green was replaced by Wallace. As he was walking towards the bench Stevens said something to Green, but Green appeared dismissive and walked towards the end of the bench. Later, Bass came out of the game and Green appeared to say something to him. That's where the verbal "altercation" occurred. Green remained standing until the end of the game.
Oh, and this happened in the 3Q, not the 2nd.