
Nadal beat Croatian Mario Ancic 6-0, 6-3 and pronounced himself pleased with his outing.
"Mario's a big player and I'm very happy for my win today. I started playing very well the first set and had a bad game at 2-0.
"But I have to be very happy about my game today. It's the first match on clay after long time. I'm happy about everything."
Top seed Federer confessed to doubts as he trailed Spanish qualifier Rueben Ramirez Hidalgo 1-5 in the final set but managed what for another player would be a miracle by pulling through for 6-1, 3-6, 7-6 (7-1) victory in two hours, two minutes.
"I was just hoping for a better spell where I was wasn't making maybe so many mistakes, finding my attacking game was working a little bit better," said the Swiss after finishing off the unfancied number 137.
"It all came together at the right times. I'm happy I got through this match," Federer added as he recovered from two breaks down and sweeping a tiebreaker after standing two points from defeat.
"I felt a little bit slow out there today," said Federer. "My opponent played so bad in the first set that he sort of almost faked me out.
"He couldn't serve, he was making many mistakes from the baseline."
Nadal, by contrast, swept the first eight games unopposed against Mario Ancic before the Croatian got onto the scoreboard. The Spaniard moved through in an hour and a quarter.
Nadal will continue his quest for a fourth consecutive title in the principality as he faces two-time winner Juan Carlos Ferrero after the senior Spaniard put out Jarkko Nieminen 6-3, 6-3.
Second seed Nadal now owns a 108-3 clay record over the past three years, winning 17 titles during that stretch.
The 21-year-old Nadal compiled a post-1968 Open Era record 81- match winning streak on clay from 2005 Monte Carlo until losing in the final in Hamburg to Federer last year.
He has a huge ask this spring over the next month, playing as a three-time defending champion in Monte Carlo, Barcelona, Rome and Roland Garros.
Federer takes a 2-0 record into his Thursday third-round match with Frenchman Gael Monfils, a winner over Croatian Ivo Karlovic 7-6 (10- 8), 6-1.
"Tomorrow is a new match, new day, new opponent. Everything's gonna change. I hope I'm just gonna play better overall."
Fourth-seeded Nikolay Davydenko, who lost to Federer in Sunday's Estoril final when he quit with a leg injury, proving his fitness over Italian Simone Bolelli 6-2, 7-6 (7-5).
The refreshed Russia winner said he felt no ill effects during the match. "I had an ultrasound yesterday and the doctor could find nothing. I also practised twice and felt fine.
"I'm actually surprised that I won in two sets and my leg's OK."
There was more frustration for former powerhouse Marat Safin, with Russia's two-time Grand Slam champion smashing a racket late in the second set as he fell to Spain's fifth seed David Ferrer 6-2, 6-3.
Sixth seed David Nalbandian beat Olivier Rochus while seeds Mikhail Youzhny and Juan Monaco were knocked out.
By Bill Scott, dpa