Murray has been battling a hip injury since last June and has not played a competitive tennis match in nearly six months.
The Brit was due to return at this week’s Brisbane International and flew to Australia last week confident of doing so despite still struggling with his mobility on court.
But the 30-year-old was forced to pull out of the tournament at the last minute and this morning confirmed that he would be returning to the UK and missing the first Grand Slam of the year.
And Roy Erskine, Murray’s maternal grandfather, has admitted that as a family they do not know what the future holds and are worried about his condition.
“Initially, I think [we felt] disappointment,” Erskine told Scottish radio station Tay FM.
“And then when you think about it, the worry comes in that we don’t know and he doesn’t know what the situation is going to be and how it’s going to end up.
“At the moment, we can just hope that everything will go well for him and that he can return to playing tennis to the same standard as he did.”
Little more than 12 months ago, Murray reached the pinnacle of the sport, ending 2016 as world No 1 by beating Novak Djokovic at the ATP World Tour Finals.
However, the number of tournaments he had to play to reach that goal took its toll and by the time Wimbledon 2017 came around, the Scot was left unable to practice.
He limped through to the quarter-finals but was eventually dumped out in five sets by Sam Querrey, a match which remains his last competitive encounter.
Murray admitted in an emotional message earlier this week that he is considering surgery on his troublesome hip, although he is considering all available options before potentially going under the knife.
And Erskine added that at this stage, it was a hope rather than an expectation that his grandson would make a full recovery.
“It’s not easy to say [whether it will affect his career],” Erskine added.
“A lot of it is hope that everything will be okay but there’s going to be a bit of anxiety until we hear exactly how he’s doing.”