All five are still entered in the Australian Open, but only Raonic is scheduled to play a warm-up tournament, with his first match in Brisbane set for Wednesday.
Murray, who slipped from the first spot to 16 on ATP rankings in 2017, will have to produce a special effort if he is to reach the final stages of the season's first Grand Slam, provided he gets fit in time.
The Scotsman endured the second half of past year facing a battle to regain fitness following a hip injury picked up at the French Open during the summer.
The latest setback will be a huge blow to double Wimbo champ Murray, who on Sunday said he felt in great shape at the start of the new season.
"I have always enjoyed competing in front of the Queensland fans".
Barring a miraculous recovery in the coming days, Murray looks destined to join fellow "Big Four" members Rafael Nadal (back) and Novak Djokovic (elbow) in missing the year's opening grand slam in Melbourne starting on January 15.
"I haven't seen that before and the year before, Rafa (wrist) and Roger (Federer, knee) missed significant periods as well".
Muguruza's run of injury woes in the tournament dates back to 2015 when she withdrew on the eve of the event with an ankle problem, before a left foot injury ended her 2016 campaign and a right thigh problem led to her semi-final retirement past year.
Murray featured in an exhibition match at Mubadala Tennis Championship in Abu Dhabi last month. Continuing rehab is one option and giving my hip more time to recover.
He is now reassessing his options with more rehab as his top choice and then surgery as a second choice due to the lower probability of a successful outcome than he would like. "There comes a point after so much rehab where you need to get back to competing again". "I would love to be number one in the world, but I just want to play".
"The hard thing with a long rehab is that it's not a simple progression where you get better and better".
The despair that the three-times grand-slam title victor is...
Australian Open is just a fortnight away and the chances are that we might not be able to see Andy Murray in action.