The Spanish top seed, who won a seventh straight Monte Carlo Masters crown on his favored clay surface on Sunday, is bidding for a sixth title in the Catalan capital in seven years.
He took his winning record on the red dust since 2005 to 183-6 to set up a clash with Frenchman Gael Monfils.
"Beating Giraldo 6-3, 6-1 is good news because he can hit winners from anywhere on the court," the Wimbledon, French Open and US Open champion said in an interview with Spanish TV.
Looking ahead to Friday's clash with seventh seed Monfils, who beat compatriot and ninth seed Richard Gasquet 6-4, 7-6 earlier on Thursday, Nadal added: "It's going to be a very tough match. Monfils is one of those players who can attack as well as defend and you never know how he is going to come out and play.
"He'll probably have to come out and attack but I'll try to dominate the points with my drives." Fourth-seeded Spaniard David Ferrer, beaten by Nadal in the Monte Carlo final, eased through to the last eight with a 6-3, 6-2 success against Victor Hanescu of Romania.
Ferrer will next meet Austrian Juergen Melzer, the sixth seed, who had to come from a set down to get past 11th seed Albert Montanes, another Spaniard, 6-7, 6-3, 6-2.
Nicolas Almagro, also of Spain, is projected to break into the top 10 for the first time on Monday if he beats Russia's ex-world No.3 Nikolay Davydenko later on Thursday.
