Andy Murray could miss the tournament in Brisbane he had been targeting for a comeback, according to reports.
Because of a hip problem, the three-time grand slam winner has not played competitively since making a quarter-final exit at this year's Wimbledon.
Murray had hoped to be fit for the 2018 season kick-off with an appearance at the Brisbane International, which starts on December 31, ahead of the Australian Open that begins on January 15.
But it has been reported that, with the Scot still in the UK, concerns are growing that he is behind schedule in his preparation and may not be ready for the start of the season.
Press Association Sport understands Murray is planning to be in Australia soon, although a specific timetable has yet to be released for him.
The 30-year-old played an exhibition match against Roger Federer at his Andy Murray Live charity event in Glasgow last month.
And the Scot was quoted by a number of national newspapers as saying at that time: "My plan is to do a couple of weeks in Miami and then go to Australia very early, much earlier than I have done in the past.
"Coming into the beginning of the new year I will be at a bit of a disadvantage because I have not played matches for a long time.
"So, if I can go there a bit earlier to get used to the conditions, a bit sooner than some of the other players, that might help level it up a bit."
Murray also said at that time: "Things have been going pretty well so far in the rehab, but you just never know.
"I've been training for a few weeks now. Some days I've felt great and some days not so good.
"But I will come back when I'm ready and when I'm 100 per cent fit. I probably made a bit of a mistake trying to get ready for the US Open but it was the last major of the year and I wanted to give it a go.
"And now it's time to give my body the rest and recovery it needs. I'll come back when I'm ready."
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