After a 1-1 draw in the first leg in Madrid, both sides have won all their games since, but Real have had to play a game more than United.
Jose Mourinho's side are still a mighty 13 points adrift of Barca at the top of La Liga, while United's demolition of Norwich at the weekend means that they are now 15 points clear of Manchester City at the Premier League's summit.
Red Devils boss Sir Alex Ferguson will find it difficult to leave out Danny Welbeck after the forward's goal at the Bernabeu, and he could employ the same playmaking trio of Welbeck, Wayne Rooney and Saturday's hat-trick man Shinji Kagawa behind striker Robin van Persie.
The veteran Welshman was left out of the squad altogether on Saturday despite plenty of buildup for the landmark match and this suggested that he would feature against Real.
Possible starting lineups
United: De Gea; Rafael, Ferdinand, Vidic, Evra; Carrick, Giggs; Welbeck, Kagawa, Rooney; Van Persie
Madrid: Lopez; Ramos, Pepe, Varane, Coentrao; Khedira, Alonso; Di Maria, Ozil, Ronaldo; Benzema
Sports Mole says: 1-2