The centre-back has stressed that his Real Madrid team-mate is a striker to be reckoned with and knows only too well of the qualities in his armoury
The Real Madrid striker has been struggling to find his best form for the national side in recent games and has been heavily criticised for his profligacy in front of goal.
Nevertheless, Ramos has insisted that Benzema cannot be underestimated as he feels the striker can single-handedly decide a match.
"Doubting a footballer like Benzema is madness. He's an outstanding striker for Madrid and France who can turn a match around," Ramos told AS.
"Everyone is free to think what they want, but when he's on form there are few strikers who are as good as him.
"You have to be very focused facing him, because if you make one mistake he'll score against you."
Spain currently sit second in Group I, trailing leaders France by two points.