Ferrero teetered two points from defeat as Gaudio, a winner of back-to-back tournaments last year in Barcelona and Mallorca, Spain, came close to giving this tournament yet another upset.
But the 22-year-old Spaniard from Valencia steadied, breaking Gaudio's serve in the second set, and then relying on a sharp forehand in the third.
"I was a few points from a loss, so I'm happy to get through this match," Ferrero said. "I started hitting my forehand longer in the third set and that made a big difference against him."
A French Open finalist from 2002, Ferrero is playing for the first time this spring on his favorite clay surface. He next faces compatriot Alberto Martin, who defeated Fernando Vicente 6-4, 7-6 (7-5) on Thursday.
"I've been playing very well lately, and I have a lot of confidence," said the former Monte Carlo and French Open champion. "I feel very at home here. But there are still two matches to win to get into the final. It's not automatic that it will be Ferrero and I again here. But it is a pleasure to play right now. I'm really hungry to win."
Moya's opponent Friday will be Julien Boutter of France, who beat ninth seed Sjeng Schalken, 7-6 (7-3), 6-4 on Thursday.
The 29-year-old Boutter claimed his first title last weekend in Casablanca.
Italian qualifier Filippo Volandri continued his amazing run on the clay, downing Sweden's Magnus Norman, 7-5, 6-3.
The last Italian to have success here was Andrea Gaudenzi, who reached the semifinals in 1995. Corrado Barazzutti reached the 1978 final while Nicola Petrangeli won the title 35 years ago.