The Dutchman missed training last week due to a virus but was cleared to play in a rematch of last season's 6-1 mauling at the same stage by the Spanish club.
"I am eager to play," Huntelaar told reporters on Tuesday. "I can finally play again on Wednesday and I am happy about that," said the forward, who is still sitting out a red card suspension in the Bundesliga.
"We simply gave away our last home game against Real (last season). We need to tackle this game better this time," said Huntelaar, adding his lack of league action since earlier this month has not dulled his scoring abilities.
Schalke coach Roberto Di Matteo must start with 19-year-old keeper Timon Wellenreuther after he confirmed that Fabian Giefer will not be fully fit in time for the game.
Wellenreuther, the third-choice keeper, wins the nod for his Champions League debut as Ralf Faehrmann is also out injured. The teenager has made three league appearances this season, starting the last two games for the club.
"We are playing against the reigning champions but we will still go into the game with the aim of winning it," Di Matteo told reporters.
"It is going to be a test for us to see how far we have developed in the past weeks and months."
The Italian, who took over in October, has put Schalke's season back on track and has seen his team lose just twice in the last 11 league games as they climbed to fourth in the Bundesliga.
"We want to take advantage of the very few weaknesses Real has," said Di Matteo, who won the trophy as caretaker Chelsea coach in 2012.
(Reporting by Karolos Grohmann editing by Ed Osmond)
