"I don't know about this game," said Buttner, when asked about the shock reverse.
"I was not here and no-one has spoken about it. It won't happen again."
"I know games like Sunday are very important for the club and supporters," he added.
"I do know there was one goal in the game at City last season, and that is why they were champions.
"If we want to be the champions this season we will have to win this game.
"We will do everything in our power to do this."