Poland's Iga Swiatek continued her terrific run with a 6-3 6-3 win over Petra Kvitova on Wednesday to reach the Miami Open semifinals, while Norway's Casper Ruud upset men's second seed Alexander Zverev in their quarterfinal clash.

Norwegian sixth seed Ruud secured the biggest win of his career with a 6-3 1-6 6-3 triumph over world No. 4 Zverev. 

After Zverev leveled the match, it was Ruud who was the aggressor in the decider as he frequently approached the net with great success, held tough during baseline rallies and limited his unforced errors. 

"I didn't hit any clean return winners but I was able to return a little bit deeper and make him play a little bit more from further behind in the court," said Ruud, who failed to win a set against Zverev in two previous meetings. 

"A couple of breaks, a couple of points that can decide a match like this and today it went my way," Ruud added.

Up next for him will be Argentine Francisco Cerundolo, whose dream run in his ATP Masters 1000 debut continued after Italian ninth seed Jannik Sinner was forced to retire from their match with foot blisters. 

Cerundolo, who is ranked 103rd, was leading 4-1 when Sinner decided to retire and becomes the lowest-ranked men's singles semifinalist in the tournament's history.

In the women's court, Swiatek, who came to Miami full of confidence after claiming back-to-back titles at Doha and Indian Wells, pressured twice Wimbledon champion Kvitova's serve throughout the 77-minute match and never faced a break point. 

The Polish second seed, who will take over the world number one ranking next week, has now won 15 consecutive matches dating back to Qatar and will next face 16th seed Jessica Pegula, who advanced after Spanish fifth seed Paula Badosa retired with a viral illness while trailing 4-1.