Roger Federer took his 2017 record to 15 wins from 16 matches as he beat Juan Martin del Potro at the Miami Open.
The Swiss, 35, won 6-3 6-4 to reach the last 16, where he will face Spanish 14th seed Roberto Bautista Agut.
“I feel like I earned it more,” said Federer, the champion in 2005 and 2006. “I was more the aggressor. It was more my racket, and I like it that way.”
In the women’s singles, German top seed Angelique Kerber beat Risa Ozaki of Japan 6-2 6-2.
Twelfth seed Caroline Wozniacki of Denmark progressed after Spanish sixth seed Garbine Muguruza retired when feeling dizzy in the heat at 7-6 (7-1) down.
“I started normal, and then like at 3-3 or something like this I started to feel headache, pain in my stomach,” said Muguruza. “And then it kind of went more and more during the match.
“When I was getting to the 5-4, something like this, I started to feel a little bit dizzy. I think it was the heat? The heat affected me suddenly like that.”
Wozniacki will next face Czech Lucie Safarova, who beat Slovakian fourth seed Dominika Cibulkova 7-6 (7-5) 6-1, while Czech second seed Karolina Pliskova brushed aside compatriot Barbora Strycova 6-1 6-4.
In the men’s singles, Czech 10th seed Tomas Berdych beat Luxembourg’s Gilles Muller 6-3 6-4 and goes on to play Frenchman Adrian Mannarino.