Rafa facing left-back headache in Russia
Benitez will be without his regular left-back choices on Thursday when Chelsea aim to protect their 3-1 advantage from last week's first leg in London.
First-choice Ashley Cole is injured while Ryan Bertrand, who has deputised for the England defender in recent games, will miss the match because of a virus.
That leaves Benitez with 18-year-old Ake, although the manager said he could also deploy experienced centre-back David Luiz on the left side.
"It's not ideal to lose a player but we're confident that we'll do the job and go through," Benitez told reporters.
"David was playing as a left-back before so maybe he can be an option. I have an idea. We'll train today and I see how everything is going and after that I'll decide for tomorrow.
"I also don't think it will be a problem for Nathan if he has to play tomorrow. He has played for us before so he can do it as well," the interim manager added.
Benitez also said playing on the artificial Luzhniki turf would not be a problem for his team.
Former Chelsea manager and long-time Benitez nemesis Jose Mourinho once famously stated that European Cup matches should not be played on a "plastic" surface but the Spaniard disagreed.
"Each country has its own conditions," he said.
"Here they have a synthetic pitch, so we'll have to play on a synthetic pitch. That is no problem for us.
"My players really want to do well. We want to win tomorrow and then go to the final and win the final," he said.