Serena Williams has withdrawn from the Italian Open with left knee pain but is confident of being fit for the French Open.

The 23-time grand slam singles champion had been due to face sister Venus for the 31st time after beating Rebecca Peterson in the first round on Monday.

Williams said on “I must withdraw from the Italian Open due to pain in my left knee. I will miss the fans and competition at one of my favourite tournaments.

“I’ll be concentrating on rehab and look forward to seeing you all at the French Open and next year in Rome.”

The Italian Open was only Williams’ fourth tournament of the season and she will head to Paris having played just eight completed matches in 2019.

The 37-year-old took nearly two months off after withdrawing ahead of her second match in Miami in March, also with knee pain, while she retired mid-match in Indian Wells earlier that month because of illness.

The only other tournament Williams has played was the Australian Open in January, where she led Karolina Pliskova 5-1 in the deciding set in the quarter-finals only to suffer the most dramatic collapse of her career.

Williams, currently ranked 11th, made her grand slam return in Paris 12 months ago following the birth of her daughter and reached the fourth round before withdrawing ahead of a much-anticipated clash with Maria Sharapova because of a shoulder problem.

The French Open begins on May 26.

Caroline Wozniacki was also a casualty in Rome as she had to retire midway through her battle with Danielle Collins.

Karolina Pliskova was in fine form in Rome
Karolina Pliskova was in fine form in Rome (Ettore Ferrari/AP)

The Dane, who suffers from rheumatoid arthritis, lost the first set on a tiebreak to the American but then withdrew with a leg injury.

Former French Open champion Jelena Ostapenko also pulled out of her game with Mihaela Buzarnescu on the brink of defeat, calling it quits when she was trailing 6-2 5-4.

Defending champion Elina Svitolina’s campaign is over as she threw away a chance of victory in a rain-delayed match against Victoria Azarenka.

Svitolina had match point in the final set against the former world number one, but fluffed her lines, allowing Azarenka to win the final four games and take a 4-6 6-1 7-5 victory.

Fourth seed Karolina Pliskova enjoyed a better time of it as she coasted past Ajla Tomljanovic 6-3 6-3.

Earlier, there were also wins for Ashleigh Barty, Kristina Mladenovic and Belinda Bencic.