You've made that up completely, he never said that he wanted to leave on the pitch. His "I stay" comment was made on the pitch after the game:
"Asked after the match where his future lay, Ronaldo told BBC TV: "I stay."
"However, the Portuguese star then told Radio 5 Live: "I don't promise nothing. I don't promise nothing to my mum, I don't promise nothing to supporters."
"He added: "I want to stay but the future - no-one knows. I want to stay. We are going to see in the next two weeks, I don't say I make a decision.""
http://news.bbc.co.uk/sport1/hi/football/teams/m/man_utd/7414182.stm