Ronaldo left Utd for Madrid in 2008
Manchester United face Real Madrid at the Santiago Bernabéu in the first of a double leg encounter of the Champions League last 16 draw.
It is the first time the two sides meet in nine years, when Real Madrid defeated United 6-5 on aggregate in the tournament's memorable 2002-2003 quarter-finals.
Defender Rio Ferdinand, who was part of the squad that lost in 2003, tweeted "Oh yes, Madrid!! What a great couple a games that'll be! @Christiano see u soon bro!"
The second leg, set to take place in March, will see Christiano Ronaldo return to Old Trafford for the first time since he left the club to join the Spanish giants for £80 million in 2008.