Norway’s Casper Ruud has upset men’s second-seed Alexander Zverev in their Miami Open quarter-final to secure the biggest win of his career.

The Norwegian triumped 6-3 1-6 6-3 over world No.4 Zverev.

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

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“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 in two previous meetings against Zverev.

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

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 last year’s runner-up Sinner decided to call the match and becomes the lowest-ranked men’s singles semi-finalist in the tournament’s history.

“I didn’t know anything,” Cerundolo said in his on-court interview.

“When I was serving at 3-1, 30-0, I saw him bending down. It was really strange.

“I didn’t see anything wrong and I hope he is OK, he is a great player.”

Italian Sinner’s nightmare blisters meant world No.103 Cerundolo’s dream run continued, as he reached the semi-final in his first Masters 1000 main draw.

“It means a lot (to advance). It is everything I have dreamed of,” said Cerundolo, who had an 0-2 main-tour record on hardcourts before this tournament.