Head fractured his left hand when he was struck on the hand by a rising delivery by Proteas paceman Gerald Coetzee while batting for Australia's run chase in the fourth ODI on Friday.
McDonald revealed that Head will not require surgery after fracturing a joint on his left hand during the fourth ODI in Pretoria. However, it is uncertain if the opener will be able to participate in the upcoming 50-over event in India as he needs over a month to recover.
"The timeframe is still a bit loose at the moment but the good news is he doesn't require surgery as it sits at the moment. There will be an extended period of time out and we've just got to weigh up whether that time (out) falls with an option to carry him through the front half of the World Cup.
"There's no doubt he won't be available for the front half, so that's a decision we'll have to make for the final 15-player squad. But I can't give you an exact time frame," McDonald was quoted by Cricket.com.au website.
Head's injury has opened doors for Marnus Labuschagne, who has surged back into favour after finishing as the South Africa series' leading run-scorer with 283 at an average of 70.75.
"I can't talk on behalf of the selection panel and lock him away in the World Cup 15 but it's no doubt looking likely," McDonald said of Labuschagne's World Cup hopes.
"He's made a significant shift in his intent at the crease and putting the bowlers under pressure (more) than he was potentially 12 months ago. He's struck at around 100 strike-rate in this series.
"We know Marnus is a quality player and he probably didn't have the 12-18 months in one-day cricket that he would have liked. But he's no doubt taken that opportunity with both hands and there's no doubt he'll be front and centre when it comes to that 15-man squad down the track," said McDonald.
Australia suffered two more injuries during the fifth and final ODI at Wanderers ground, with pacers Nathan Ellis and Sean Abbott picking up fresh injuries.
Ellis suffered an adductor strain and was unable to finish his spell after sending down eight overs and is set to be assessed further.
Abbott split the webbing on a finger while fielding and required stitches, but was able to complete his spell and McDonald suggested he should be right to face India in the upcoming series.
Aaron Hardie will travel from South Africa to India with the ODI squad as cover for the pair. Teams can make changes to their World Cup squads right up until the 28 September deadline.