Iga Swiatek, of Poland, serves to Coco Gauff, of the United States, during the first set during the Miami Open tennis tournament, March 28, 2022, in Miami Gardens, Florida. (JIM RASSOL / AP)

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 semi-finals, while Norway's Casper Ruud upset men's second seed Alexander Zverev in their quarter-final clash.

Iga Swiatek, who came to Miami full of confidence after claiming back-to-back titles at Doha and Indian Wells, pressured twice Wimbledon champion Petra Kvitova's serve throughout the 77-minute match

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 No 1 ranking next week, has now won 15 consecutive matches dating back to Qatar and will next face 16th seed Jessica Pegula.

"I want to use the confidence that I built since the beginning of Doha," said Swiatek.

"I'm on a roll and I want to use that. Having that kind of streak got pretty tricky, but I'm pretty glad that I could play well, that I'm healthy, and that I can compete against players like Petra. She's a legend."

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Pegula advanced after Spanish fifth seed Paula Badosa retired with a viral illness while trailing 4-1.

"Been struggling with illness since the last match the other day," Badosa wrote on Twitter. "Tried everything to recover but wasn't enough. I'll take some days to recover well and prepare for clay court season."

For Pegula, it marked the second consecutive abrupt ending to a match as unseeded Ukrainian Anhelina Kalinin retired while down 6-0 in their fourth-round clash.

Casper Ruud, of Norway, celebrates after defeating Alexander Zverev, of Germany, during the Miami Open tennis tournament, March 30, 2022, in Miami Gardens, Florida. (MARTA LAVANDIER / AP)

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.

Ruud had failed to win a set in two previous meetings against Zverev.

"I feel a little bit good. I mean, it's obviously an exciting night and the biggest win of my career so far," Ruud told reporters.

"This is now the fourth time I'm reaching a semi-final in a Masters 1000 event and ... the first time on hard court so that means it's a little bit extra special for me."

Alexander Zverev, of Germany, walks off the court after losing to Caster Ruud, of Norway, during the Miami Open tennis tournament, March 30, 2022, in Miami Gardens, Florida. (MARTA LAVANDIER / AP)

Ruud lost the three Masters semi-finals he previously played in Rome, Monte Carlo and Madrid — all claycourt tournaments.

"Let's see if I can take what I have learned from the three previous semi-finals where unfortunately I lost all of them and see if I can turn it around and make the fourth time the lucky charm," he added.

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Up next for Ruud 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 call the match and becomes the lowest-ranked men's singles semi-finalist in the tournament's history.