The retired 36-year-old Netherlands forward played for both clubs during the peak of his club career between 2001-10 and found it difficult to pick a favourite for the tie
Former Manchester United and Real Madrid striker Ruud van Nistelrooy says it is “impossible” to choose between the two sides after they were paired together in the Champions League last 16 draw.
The undoubted glamour tie of the round will see Cristiano Ronaldo return to Old Trafford for the first time as a player since his departure in 2009, with the first leg on February 13 at Bernabeu before the second leg at Old Trafford on March 5.
THE DRAW IN FULL
Galatasaray v Schalke
Celtic v Juventus
Arsenal v Bayern Munich
Shakhtar v Borussia Dortmund
AC Milan v Barcelona
Real Madrid v Manchester United
Valencia v Paris Saint-Germain
Porto v Malaga
First legs will be played on either February 12/13 or19/20, with the return legs on March 5/6 or 12/13.
"United or Madrid… Who do I want to win? Played my heart out for them both. Proud to have played for both. #impossible #MayTheBestTeamWin," Van Nistrelrooy tweeted.
Despite the stature of the two sides, their domestic campaigns are not identical; United are currently top of the Premier League table, six points clear ahead of nearest rivals Manchester City, while Real Madrid sit 13 points behind Barcelona in third.