Monaco, who ousted Raonic in the previous round, took a 2-1 lead in the first set. But that was as far as he could get on this day, Nadal capturing the following 17 games and storming to an unbelievable victory.
In the quarters, Nadal will face fellow countryman Nicolas Almagro, who eliminated Serbian Janko Tipsarevic also in straight sets 6-4 6-4 6-4.
No.4 seed Andy Murray also booked his place in the last 8 after overcoming Frenchman Richard Gasquet 1-6 6-4 6-1 6-2.
Gasquet looked very strong from at the beginning of the match, taking the first set in just 29 minutes.
Murray seemed to be in all sorts of problems, clutching his lower back signalling that the injury that has caused him trouble earlier has returned.
But the British no.1 managed to hang in there and after taking the second set, he broke Gasquet’s resistance. The Frenchman couldn’t find any answers to Murray’s aggressive game and there was no way back for him into the match.
Murray’s next opponent will be in form playing Spaniard Ferrer, who ousted his countryman Granollers 6-3 6-2 6-0.