Real are in crisis this weekend ahead of facing Osasuna.
Morientes said on Cadena Cope: "I don't have the magic wand... I think it's a fundamental problem.
"It's a matter of slightly underestimating the progress of one of the leaders in the midfield. We've talked about it a thousand times and heard it in countless debates... which is Toni Kroos.
"In the big teams I always imagine two players per position. For example, if you play with a 4-4-2 with four powerful forwards. In our time, if you weren't doing well, you had to make changes and in the end this made you train better and want to return to the team again.
"Not having four reliable centre-backs is a handicap if anything happens. You can't imagine (Aurelien) Tchouaméni as a centre-back, even though he is a big, strong and powerful guy. And the centre-backs can tell you that.
"I can't imagine a midfielder as a striker because strikers have a completely different job to everyone else."
Morientes says Ancelotti should also rethink his limited selection of young pair Endrick and Arda Guler.
"Endrick came on for two moments and scored two goals... well, he could score another 90! There's Güler... It's a question of going over the team and finding things that haven't been found yet."