Veteran American becomes second top 30 player to skip Australian Open

Tennys Sandgren had been originally diagnosed with Covid-19 in November

In a flurry of tweets, the world No.50 said that he might be able to catch another flight the following day, before suddenly informing his followers that he was on the plane destined for the Australian Open.

Andy Murray has tested positive for the coronavirus days before he was due to leave Britain for the Australian Open, a person with knowledge of the situation told The Associated Press on Thursday.

The three-time Grand Slam champion is isolating at home near London, the tournament said in a statement.

The Australian Open was delayed three weeks because of COVID-19 restrictions and is set to begin February 8. There are 104 direct entries based on rankings for the men's and women's singles main draw, plus wild-card entries and the qualifiers. "And of course, that wouldn't be the case for Australia this year", Isner said after falling to fellow American Sebastian Korda in the quarter-finals of the Delray Beach Open in Florida.

All players and officials are only allowed to bring a small amount of support staff with them to Melbourne for this year's event due to the strict COVID-19 quarantine requirements in place to ensure the event goes ahead.

Sandgren sent out a series of tweets before his departure from Los Angeles, initially saying he had tested positive on Monday and would miss his flight.

Sandgren received an exemption after Australian health officials assessed his case history.

While a positive test threatens Murray's participation in Australia, it doesn't necessarily rule it out. "I'm staying home." Isner, 35 and a father of two, says it was a hard decision to make.

Organisers Tennis Australia were not immediately available to comment.

The first players contesting the Australian Open are scheduled to arrive in Melbourne this evening.

A spokesman for Covid-19 Quarantine Victoria said it was common among people who had previously tested positive to "shed viral fragments for some time - which can trigger another positive result".

The players, who will be allowed to spend five hours outside their rooms during quarantine for training purposes, will then play warm-up events at Melbourne Park from Jan 31 before the Australian Open starts on Feb 8.