John Isner was broken in the first game but he held the rest of the way and hit 16 aces to beat Albert Ramos-Vinolas 7-5, 7-6 (6) Sunday in the third round of the Miami Open.

Isner, now 33, won the biggest title of his career in the tournament a year ago. He is seeded seventh this year.

Isner will next face No. 19-seeded Kyle Edmund, who beat No. 12 Milos Raonic 6-4, 6-4.

In women's play, Venus Williams reached the fourth round of the tournament for the 16th time with a 6-3, 6-1 win over No. 14 Daria Kasatkina, who never held serve.

Williams won the title in 1998, 1999 and 2001. She's unseeded at Miami for the first time since 2012, but improved to 11-3 this year.

Williams next faces No. 2 Simona Halep, who outlasted Polona Hercog 5-7, 7-6 (1), 6-2.

"I was running like crazy for three hours," Halep said. "If I keep doing this, I think I have a chance to be back No. 1."

A loss Saturday by top-ranked Naomi Osaka opened the door for Halep to reclaim the top ranking if she reaches the final.

No. 25 Danielle Collins lost to Wang Yafan 7-5, 6-1.