World number five Andrey Rublev is the fifth player to test positive for COVID-19 after playing at an exhibition event in Abu Dhabi this month.
Spaniard Rafael Nadal, Canadian Denis Shapovalov, Switzerland's Olympic champion Belinda Bencic and Tunisian Ons Jabeur all tested positive after taking part in the event.
US Open champion Emma Raducanu tested positive in Abu Dhabi before the event and withdrew, while Nadal's coach Carlos Moya also contracted the novel coronavirus.
The 24-year-old Rublev, who beat Andy Murray in the World Tennis Championship final on December 18, confirmed on Twitter he was isolating with minimal symptoms.
"I am currently in Barcelona and unfortunately tested positive for COVID-19," the Russian said. "I am in isolation and following all the protocols under the supervision of doctors.
"As you know, I am fully vaccinated and was preparing for tournaments – ATP Cup and Australian Open. Now I have to recover and I will go to Melbourne only when it will be safe for everyone."
The Australian Open will be held at Melbourne Park from January 17. Rublev was part of the Russian team that won the men's ATP Cup this year and had been included in the team for the upcoming edition in Sydney, which kicks off on Saturday.
Formula One stewards handed Haas rookie driver Oliver Bearman a 10-place grid drop for his first home British Grand Prix for failing to comply with red warning flags in Saturday's final practice.
Seventh seed Mirra Andreeva outclassed American Hailey Baptiste 6-1 6-3 under the Court One roof to equal her best Wimbledon run by reaching the last 16 on Saturday.
Carrying a red floral wreath bearing his shirt number, Diogo Jota's Liverpool teammates joined relatives and residents in a small Portuguese town on Saturday for the funeral of the football star, who died with his brother in a car crash on Thursday.
An 83rd-minute Weverton own goal from a deflected Malo Gusto cross gave Chelsea a nervy 2-1 win over a spirited Palmeiras side in the Club World Cup quarter-finals on Friday.
Women's top seed Aryna Sabalenka fought off inspired home favourite Emma Raducanu in a cauldron-like Centre Court atmosphere to keep her Wimbledon quest on track but it was the end of the road for two other Grand Slam champions on Friday.