Roger Federer reached the fourth round of the Miami Open on Monday with a 6-3, 6-4 victory over 29th-seeded Argentine Juan Martin del Potro in Key Biscayne, Florida.

Roger Federer, Angelique Kerber Advance In Miami Open

The fourth-seeded Swiss, who was playing del Potro for the first time since 2013, never lost serve and improved to 15-1 this year. Federer, 35, broke the Argentine twice, once in each set.

Federer, who now boasts 15 victories in 16 matches in 2017, next faces 14th-seeded Spaniard Roberto Bautista Agut on Tuesday’s Round of 16. Agut defeated 22nd-seeded American Sam Querrey 3-6, 6-2, 6-3.

“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.”

The other third-round winners in the men’s singles were Swiss top-seed Stan WawrinkaDavid Goffin, Tomas Berdych, Nick Kyrgios and Alexander Zverev.

Wawrinka, who has never won the tournament, beat Tunisia’s Malek Jaziri 6-3 6-4, while 12th-seeded Australian Kyrgios defeated 17th-seeded Croatian Ivo Karlovic in a deciding tie break 6-4 6-7 (4-7) 7-6 (7-2). He next faces 16th-seeded Zverev, a 19-year-old German who beat 18th-seeded American John Isner in three sets, all tie-breakers.

Czech 10th seed Berdych beat Luxembourg’s 24th-seed Gilles Muller 6-3 6-4 and will next face Frenchman Adrian Mannarino. 

On the women’s side, top-seed Angelique Kerber reached the quarterfinals by beating Japan’s Risa Ozaki, 6-2, 6-2. The German next faces 11th-seeded Venus Williams, who defeated seventh-seeded Russian Svetlana Kuznetsova , 6-3, 7-6 (4), in a matchup of former Miami Open winners. Williams last won the tournament in 2001.

One shocking women’s upset was sixth-seeded Garbine Muguruza, who retired after just one set against 12th-seeded Caroline Wozniacki of Denmark after feeling dizzy from the heat. The 23-year-old Venezuelan-born Spaniard and 2016 French Open champion was tended to by doctors after 70 minutes of play, and lost 7-6 (7-1) to Wozniacki.

“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 Lucie Safarova, who beat Slovakian fourth seed Dominika Cibulkova 7-6 (7-5) 6-1.

KEY BISCAYNE, FL – MARCH 27: Roger Federer of Switzerland returns a shot against Juan Martin Del Potro of Argentina during Day 8 of the Miami Open at Crandon Park Tennis Center on March 27, 2017 in Key Biscayne, Florida. (Photo by Al Bello/Getty Images)

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