Real Madrid superstar Cristiano Ronaldo was a "show pony" when he arrived at Manchester United, according to former team-mate Rio Ferdinand.

Ronaldo equalled Madrid's all-time goalscoring record with a brace in its 2-0 win over Malmo in the UEFA Champions League on Thursday (AEST).

But when he arrived at Old Trafford from Sporting Lisbon ahead of the 2003-2004 season, Ronaldo was yet to make a name for himself.

Ferdinand, who was at United throughout Ronaldo's six-season stay at the club, said the Portugal star has developed from a bag of tricks to a true great of the game.

"When he came to Manchester United, he was a show pony," Ferdinand told BT Sport.

"He wanted to do skills, he wanted to show people how good he was and take people on, take the mickey out of full-backs.

"Then he realised it was about end product and to become the best player in the world it would be all about purely scoring goals, or setting goals up for others and having an impact on games. He's forced himself to become that guy.

"He's been relentless season upon season, raising the bar. That's greatness right there."

Ronaldo could surpass Raul's mark of 323 goals for Madrid when it visits rival Atletico Madrid on Monday (AEST).