Nadal had a bye in the first round after defeating Novak Djokovic in the Monte Carlo Masters final on Sunday and improved to 31-1 on the clay in Barcelona after breaking his fellow Spaniard six times.
"My knee bothered me a little, but that's normal. In 15 days, the discomfort isn't going to go away, but it doesn't keep you from playing so it's not a problem," said Nadal, who had to withdraw before the semifinals of last month's Sony Ericsson Open because of a left knee problem. "I made few errors, my backhand was good and my forehand allowed me to vary my game and it helped me a lot."
Fellow Spaniard David Ferrer needed less than an hour to advance to the third round by beating Serbian wild card Filip Krajinovic 6-0, 6-3. The sixth-ranked Ferrer is bidding for his first Godo trophy after finishing as the runner up three times.
"Rafa is, without a doubt, the favorite because he is the best player of all time on clay, but he can also lose," Ferrer said. "Every player has to focus on the rival in front of him now rather than further ahead."
Seventh-seeded Feliciano Lopez of Spain also reached the third round with a 6-4, 6-3 victory over Italy's Flavio Cipolla and will face Jarkko Nieminen of Finland, who won 6-3, 6-7 (4), 6-4 over Eduardo Schwank of Argentina.