"It's good to have that kind of problem as the three centre-backs are playing really well now," said Sir Alex. "I'll make that decision tomorrow – hopefully it's the right one – but I couldn't be happier with the three of them."
The anticipation is building ahead of the Old Trafford encounter with the focus of the world's media trained on Manchester.
"It's a massive build-up," said Sir Alex. "You can see from the number of photographers at the training ground that it's an indication of how important a game it is for both clubs. It's an occasion you always want to have and that's the beauty of the Champions League, you have the opportunity each year to play against one of the big teams from Europe. Tomorrow is one of the biggest."