The confrontation happened during a timeout early in the second half of Cal's 76-68 win over Southern California on Sunday night when Montgomery yelled at star guard Allen Crabbe for nonchalant play and then shoved him in the chest with both hands.
Crabbe had to be forcibly restrained by teammates and briefly left the court before coming back and leading a comeback victory for the Golden Bears (16-9, 8-5 Pac-12).
"Sunday's game was an emotional one for everyone who cares deeply about our men's basketball program, and the Bears certainly showed tremendous resolve coming back to earn a win over USC," Barbour said in a statement. "However, it is unacceptable for our coaches to have physical contact with student-athletes regardless of the circumstances. The second-half incident was certainly out of character for Mike Montgomery, and I am confident that something like this will not happen again."
Montgomery downplayed the controversy during a postgame news conference when he smiled and said the move motivated Crabbe. He also said he would do it again.
"Worked, didn't it?" Montgomery said of the exchange with Crabbe. "Allen had come down twice went to the wrong side of the court and his guy shot two 3s. I was trying to get him going. Probably overdid it a little bit but Allen's my guy. We can't win if he is not ready to play."
Crabbe, the leading scorer in the Pac-12 with an average of 19.8 points per game, scored 14 points after the shove and led the Bears back from a 15-point deficit to win.
Montgomery later apologized in a statement released by the school.
"I have great passion for this game and tonight, I let my emotions get away from me in the heat of the moment," Montgomery said. "While my intent was to motivate our student-athletes, my behavior was inappropriate and I apologize for my actions."
Crabbe said after the game that emotions were high at the time and Montgomery was just trying to motivate him.
"Everything's fine," Crabbe said. "It's under the bridge. He's my coach, no hard feelings. We're just going to keep moving on."