Five-time finalist Andy Murray will miss the Australian Open after a solution to find a "workable quarantine" following his positive test for coronavirus could not be found.
The former world number one had hoped to travel safely and compete as planned on the back of a negative test.
Murray said he was "gutted" not to go.
He was asymptomatic and is now out of self-isolation, but finding a way for him to travel to Australia and then going into quarantine before the tournament starts on 8 February proved too difficult.
"We've been in constant dialogue with Tennis Australia to try and find a solution which would allow some form of workable quarantine, but we couldn't make it work," said Murray.
"I want to thank everyone there for their efforts. I'm devastated not to be playing out in Australia. It's a country and tournament that I love."
Murray was able to play only seven official matches in 2020 because of a lingering pelvic injury, and the five-month suspension of the tours because of the pandemic.
At 123rd in the world, he was ranked too low to gain direct entry into Australian Open so the three-time Grand Slam champion was given a wildcard.
The Australian Open at Melbourne Park is starting three weeks later than usual because of the coronavirus pandemic.
Players had to test negative before taking one of the 15 chartered flights - which were put on last week by tournament organisers and operated at 25% capacity - to Australia.
On arrival, the players and their support staff went straight into a 14-day quarantine under the conditions imposed by the Australian government.
That agreement allowed them out of their rooms for up to five hours a day for food and practice.
However, 72 players have been confined to their rooms in a tougher quarantine - which led to some complaints and creative ways of staying fit - after they travelled on three flights where positive cases were found on arrival.