The Real Madrid striker has been struggling to find his best form for the national side in recent games and has been heavily criticized for his profligacy in front of goal.
Nevertheless, Ramos has insisted that Benzema cannot be underestimated as he feels the striker can 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 sits second in Group I, trailing leader France by two points.
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