The Roja goalkeeper still believes that his Blancos team-mate is one of the finest strikers in the world, even though the former Lyon man has yet to score in Poland and Ukraine
Benzema has come in for criticism from some quarters after failing to find the back of the net in Les Bleus' three games to date, but Casillas views the 24-year-old striker, who scored 21 times for Los Blancos in La Liga last season, as a very real threat to La Roja's hopes of defending their European title.
"I'm really lucky to play on the same team as him, and now destiny has pitted us against each other," the goalkeeper mused during a press conference on Thursday.
"He's a fantastic player, but I hope he has a bad game on Saturday!"
France eventually limped into the knockout stages, finishing runners-up behind England in Group D after slumping to a surprise 2-0 defeat at the hands of already-eliminated Sweden.
Consequently, many believe that the game in Donetsk will be something of a walkover for the Spanish, but Casillas insists that he and his colleagues are expecting a very tough test.
"Nobody in the team thinks it is going to be a stroll in the park or a thrashing," the World Cup winner declared. "We're going to have to work very hard to beat them."
Spain's eagerly-awaited meeting with the French will kick off at 20:45CET.