Seventh-ranked Holger Rune beat a frustrated Novak Djokovic 6-2, 4-6, 6-2 in a rain-interrupted quarterfinal at the Italian Open, where women's top seed Iga Swiatek retired injured on Wednesday.

Djokovic, who will drop to second in the world behind Carlos Alcaraz, admitted that he was outplayed in heavy, wet conditions after a week of rain in normally sunny Rome.

"This is probably the coldest, wettest tournament I've ever played here in Rome," the 22-time Grand Slam winner said.

"I don't recall so many days in a row (of) raining. In these conditions, it's very difficult to get the ball past him."

"He's a very talented, dynamic player — he was too good for me for most of the match," Djokovic added of Rune.

'This is probably the coldest, wettest tournament I've ever played here in Rome.'

With her French Open title defense looming this month, Swiatek retired in the third set of her quarterfinal against Kazakhstan's Elena Rybakina.

Poland's Swiatek had roared through the first set but after receiving treatment she called a halt with a right leg injury to hand Wimbledon champion Rybakina a 2-6, 7-6 (7/3), 2-2 win and a semifinal spot.

Victory in drizzle and evening chill came in just under two and a half hours as Swiatek's 14-match Rome win streak was ended.

Rybakina ended with 32 winners and 26 unforced errors, in a match Swiatek led by a set and 4-2.

"It's never good to win like this," Rybakina said.

"I hope it's nothing serious for Iga."

"I'm glad to win, every match I play on clay gives me more confidence," she added.

"I didn't start well but in the second set I found my rhythm."

Rybakina will now take on former Roland Garros champion Jelena Ostapenko, who defeated Spain's Paula Badosa 6-2, 4-6, 6-3.

Denmark's Rune will line up against Casper Ruud in the semi-finals after the Norwegian fourth seed defeated Francisco Cerundolo 7-6 (7/5), 6-4.

Argentina's Cerundolo committed nearly 50 unforced errors and could not prevent 2022 Roland Garros finalist Ruud from reaching a third consecutive Rome semi.

"I'm back in Rome and feeling great," Ruud said.

"I've had success in Italy."

"Maybe it's something in the food, there are a lot of reasons to be motivated here."

"It's great to be back in the semi-finals, I hope it will be a fun one."

Six-time champion Djokovic was carrying an unspecified injury into the match as he lost for a second time to the rising 20-year-old Dane, who bested him to win the Masters 1000 at Paris Bercy last November.

The latest contest between the pair was marred by spats with the chair umpire by both players — Djokovic on a time warning and Rune over a second-set line call.

Play was halted for just over an hour by rain. Shortly after the match began, Djokovic requested extra towels to pad his lower back on the bench during most changeovers.

He has also suffered with a right elbow problem in recent weeks which caused him to miss the Madrid event and put his pre-Roland Garros preparation behind schedule.

He was treated by the trainer and tournament doctor after the third game of the second set and given a painkiller before playing on.

The exit of Djokovic — combined with that of Alcaraz this week — left the men's field wide open at the Foro Italico.