After his exertions on international duty, the Brazilian playmaker was used as a second-half substitute in Saturday's 4-2 La Liga win over Valladolid, and with Cristiano Ronaldo sidelined Real will expect a match-winning performance.
Coach Manuel Pellegrini could also be without Lassana Diarra, who was unable to train with the squad on Monday after picking up a knock at the weekend, while Milan goalkeeper Marco Storari and midfielder Gennaro Gattuso have been ruled out with thigh and knee injuries respectively.
Real's wounded list includes midfielder Fernando Gago, striker Ruud van Nistelrooy and defender Christoph Metzelder, but there was some good news for Pellegrini on Monday when midfielder Guti trained as normal after recovering from an ankle problem.
Milan, who suffered a shock 1-0 home defeat by FC Zurich last month, have struggled under coach Leonardo, with the slow pace of play a particular problem, although Sunday's 2-1 win over AS Roma has eased the pressure.
Real defender Raul Albiol said Milan's poor form in Serie A this season would be irrelevant once the two European heavyweights take to the Bernabeu pitch.
"It's true that Milan are having a difficult time in their domestic league but they are a great team and they always show their best face in the Champions League," Albiol told Real's website.
"They have a lot of experience in the competition and very good players and they will be extremely tough opponents," he added. "We are playing at home in front of a full house and we want to show what level we have reached."
BEAUTIFUL THINGS
Milan striker Filippo Inzaghi, 36, is largely being kept back from Serie A action in order to use his experience in Europe but there are doubts over the formation with Leonardo switching between 4-3-1-2, 4-4-2 and 4-3-3 in recent games.
"All teams have problems, we must not believe that Milan have more problems than others. If we manage to express ourselves at our best, we will be able to do much better than what we have done so far," Leonardo told reporters on Sunday.
Brazilian Ronaldinho, still nowhere near the form he showed at Barcelona despite an improvement against Roma, will be keen to prove to the Madrid public that he can still perform.
In the 2005-06 season, he produced a sublime performance at the Bernabeu to lead Barca to a 3-0 victory, scoring two stunning solo goals in a display that brought the home crowd to their feet.
"It's a stadium in which I done some really beautiful things but now I am, and we are, in a different situation," he told Milan's TV channel.
Probable teams:
Real: 1-Iker Casillas; 4-Sergio Ramos, 3-Pepe, 18-Raul Albiol, 12-Marcelo; 24-Esteban Granero, 22-Xabi Alonso, 10-Lassana Diarra or 6-Mahamadou Diarra, 8-Kaka; 7-Raul, 11-Karim Benzema.
Milan: 1 Dida; 44-Massimo Oddo, 13-Alessandro Nesta, 33-Thiago Silva, 15-Gianluca Zambrotta; 20-Ignazio Abate, 21-Andrea Pirlo, 23-Massimo Ambrosini; 7-Alexandre Pato, 9-Filippo Inzaghi, 80-Ronaldinho.
