The Scot admits that he was "bitterly disappointed" with his players after they failed to follow his gameplan, and he felt he had no choice but to share his anger with the dressing room.
"I was angry in the first half and they did see another side to me, it was a reaction that doesn't come out very often but I felt I had to," he told the club's official website.
"We go into every game with a gameplan - what we do with the ball, what we do without the ball. With the ball we didn't do what we'd worked on. It took us 32 minutes to do that. I was bitterly disappointed.
"You don't want to be falling out with players but sometimes you have to tell them."