From his debut at Old Trafford, it was obvious United had a potential star on their hands.
Ronaldo would go on to win three Premier League titles, an FA Cup and a Champions League title under Ferguson. Between 2006 and 2009, he was close to unstoppable, scoring goals freely and earning a host of individual accolades—most notably the 2008 Ballon d'Or.
In 2009, unable to resist the temptation of joining his boyhood heroes, he moved to Real Madrid for a record £80 million.
In four seasons, Ronaldo has proved that money to be well spent. He's been prolific in La Liga and in Europe for Madrid and played the major role in their beating of a brilliant Barcelona team to claim the Spanish title in 2012.
In this clip, Bleacher Report lead writers Will Tidey and Dan Levy look at Ronaldo's two club careers so far and compare his output.