Venus Williams remains on course to meet sister Serena in the Miami Open final after upsetting world number five Caroline Wozniacki in the last 16.
The American beat her Danish opponent 6-3 7-6 (7-1) in 98 minutes.
The 34-year-old, who was out of action for seven months after being diagnosed with Sjogren's Syndrome in 2011, has now won seven of her past eight matches against top-10 ranked players.
Sister Serena beat Svetlana Kuznetsova 6-2 6-3 to reach the quarter-finals.
The 33-year-old will meet Sabine Lisicki in the last eight after the German beat Sara Errani 6-1 6-2.
Venus, meanwhile, faces Spaniard Carla Suarez Navarro, who recovered from the loss of the opening set to beat Polish seventh seed Agnieszka Radwanska 5-7 6-0 6-4.
Novak Djokovic - the top seed and defending champion in the men's draw - swept aside Belgium's Steve Darcis 6-0 7-5.
Venus back in the groove
Venus racked up her seventh consecutive victory against Wozniacki in aggressive style - hitting 37 unforced errors, but also finding 40 winners to her opponent's nine.
|Venus' 2015 top-10 scalps|
|Opponent||Ranking at the time||Result|
|Caroline Wozniacki||5||6-3 7-6 (7-1) in Miami|
|Agnieszka Radwanska||4||6-4 1-6 6-3 in Doha|
|Agnieszka Radwanska||6||6-3 2-6 6-1 in Australian Open|
|Caroline Wozniacki||1||2-6 6-3 6-3 in Auckland|
After the win, she said her self-belief had never been damaged by her spell of poor health, adding she was enjoying her sport as much as ever.
"I have always seen it as something to overcome, and not something that could stop me," she said.
"Tennis is definitely not pushing paper. You have no idea what's going to happen in the point.
"You can try to plan it the best you can, but it's all up in the air. You have to improvise every single time. That never gets boring.''
Best of the rest
Spain's David Ferrer saw off 26th seed Lukas Rosol 6-4 7-5, but fifth seed Milos Raonic was taken deep into a decider before overcoming France's Jeremy Chardy 6-1 5-7 7-6 (7-3).
Japan's Kei Nishikori, who beat Roger Federer on his way to the semi-finals last year, safely negotiated his way past Serb Viktor Troicki, winning 6-2 6-2 to reach the fourth round.
He will next face Belgium's David Goffin, who beat 2013 Wimbledon semi-finalist Jerzy Janowicz 6-4 6-3.
In the women's draw, Romanian third seed Simona Halep beat Flavia Pennetta of Italy 6-3 7-5 and will now face American Sloane Stephens, who secured a 6-4 7-6 (7-5) win over Switzerland's Belinda Bencic.
British number one Andy Murray returns to action on Tuesday in a fourth-round match with South African Kevin Anderson, which will be followed by Djokovic against Ukrainian Alexandr Dolgopolov and Venus Williams' match with Suarez Navarro.