Miami: Alexander Zverev capitalised on a fast start against Australian Nick Kyrgios to grind out a 6-4, 6-4 victory in a battle between two of the sport's brightest prospects to advance to the quarter-finals of the Miami Open on Tuesday.

The 20-year-old German is looking to win the third Masters event of his career and advanced to a last-eight showdown against Croatia's Borna Coric, who ended the run of Canadian prospect Denis Shapovalov 7-6 (7-2), 4-6, 6-4 in a tight encounter.

Earlier, big-serving American John Isner overcame second-seeded Croatian Marin Cilic 7-6 (7-0), 6-3 to advance to the quarter finals, where he will face South Korean Chung Hyeon, who dominated Joao Sousa in a routine 6-4 6-3 win.

Also advancing was Juan Martin del Potro, who defeated Filip Krajinovic 6-4, 6-2 for his 14th consecutive victory as he looks to back up his Indian Wells title triumph with another tournament win. <>"I will try to keep going and see how far I can go," said Del Potro, who next meets big-serving Milos Raonic after the Canadian cruised to a 6-3 6-4 victory against an overpowered Jeremy Chardy of France.

Del Potro beat Raonic in last week's semi-finals in California before edging out Federer in the title match.

"It'll be a difficult match," Raonic admitted."He's been the best player in the world for the past four, five weeks."

Among women, American Sloane Stephens needed just over an hour to cruise past Germany's former world No. 1 Angelique Kerber 6-1, 6-2 and reach the Miami Open semi-finals for her first time.

The US Open champion fired her 22nd winner on match point to dispatch the 10th-seeded Kerber and set up a showdown with three-time champion Victoria Azarenka, who scored a 7-5, 6-3 victory over world No. 6 Karolina Pliskova.

The win guarantees that 25-year-old Florida native Stephens will make her debut in the top 10 when the WTA rankings are released after the tournament. Reuters