Asked to pick three decisive results in the Reds' title-winning campaign, Rooney selected the late away wins over Liverpool and Fulham, but his third choice is somewhat unexpected.
"One result that stands out in my mind is losing to Arsenal at home in September," he told the latest issue of Inside United.
"We went on a brilliant run of victories after that. We lost that game and everyone was saying 'the Reds are going to stumble', but we kept on going and we were unbeaten until December in the league."
Despite a season that many people will remember for the free-flowing and exciting attacking football, Rooney says United's refusal to dwell on defeats often made a huge difference.
"That's one of the best things about this team, we're defiant in defeat," he added. "We know we can't afford to let it affect us. That comes from the togetherness of the team. We always bounce back after a loss."