The Italian announced the news at Monday's pre-match press conference (h/t ESPN FC's Dermot Corrigan):
Given that passage to the quarterfinals is something of a formality, and with El Clasico less than a week away, the decision not to rest his star striker is a little baffling.
Further confirmation that Jese and Alvaro Morata will join the Portuguese in a front three would suggest that Gareth Bale will be rested for this game.
And at 6-1 up, such a move by Ancelotti makes perfect sense.
Could it be that Ronaldo is intent on setting another Champions League scoring record?
In a week when his nemesis Lionel Messi made history, per Barcelona's official site, and could conceivably do so again at the Bernabeu, it's not beyond the realm of possibility for Ronaldo to want to steal some of his thunder.
It's still a huge risk for the Italian to take, even if Real's German opponents provide stiffer opposition than in the first leg.
So poor were Schalke at home that all three Madrid forwards ran riot, scoring two each and recording a perfect 10, per WhoScored.com.
Play as badly again and another thrashing could be in the cards.
Perhaps that is behind Ancelotti's thinking. If Madrid dominate as expected, Ronaldo can potentially help himself to goals, ensuring he is back in form ahead of Barcelona's visit.
It's a brave decision, but Ancelotti faces a huge backlash if Ronaldo gets injured on Tuesday.