Roger Federer fought through a tough first set and turned it on in the second to beat Juan Monaco 7-6 (7-4), 6-4 as the Swiss clocked his 20th win of the season to advance at the Miami ATP Masters 1000.
The third seed, who won the event at Crandon Park twice, improved his record on the season to 20-3 in a campaign dominated so far by the 20-match winning streak of second-seeded Serb rival Novak Djokovic.
Top seed Rafael Nadal followed suit as he beat fellow Spaniard Feliciano Lopez for the seventh time in nine meetings, taking a 6-3, 6-3 decision.
Federer's clean and clinical third-round victory Monday in one and three-quarters hours over the Argentine, improved his overall Miami mark to 38-10.
"It was tough not having played him very often," said the Swiss. "This is as slow as it gets out on the hard court. It's a bit of clay almost except that you can't slide.”
"I thought he played well in the later stages of the first set and then also in the second. I had a return game, which worked well, and was able to serve it out. So it was a good finish for me."
Federer will next play longtime friend Olivier Rochus, a winner over Russian Mikhail Youzhny 1-6, 6-3, 6-3.
The night session was plagued by rain showers, which resulted in two matches having to be carried over to Tuesday.
Jo-Wilfried Tsonga of France and Alexandr Dolgopolov were in the third set with Dolgopolov ahead 6-7 (2/7), 6-4, 3-2 when rain halted their match.
Kim Clijsters's night match against Ana Ivanovic was also moved to Tuesday morning.
Seventh-seeded Wimbledon finalist Tomas Berdych beat Argentine Carlos Berlocq 7-6 (10/8), 7-5. Janko Tipsarevic of Serbia beat German Philipp Petzschner 6-3, 6-3 in their third-round contest.
Germany's Florian Mayer stopped Spanish 11th seed Nicolas Almagro 6-1, 3-6, 6-1.