The Sounders played reserves players and even trialists against the European runners-up and paid the price for not taking the game on as they should have.
Garber feels that it is these types of matches which will put MLS on the map and is sure that the Sounders would now regret their decision to go in half-hearted.
"Nobody likes to lose 7-0," Garber said. "You don't like to lose 7-0 in a schoolyard soccer match.
"Our view is that if we're going to play these games, we ought to play to win. And if a team can't fit it into their schedule either because of congestion or their own priorities, then they shouldn't play in those games.
"I think Seattle regrets playing their second team, reserves, even trialists against Manchester United. I don't think we'd ever do anything like that again."