The Ulster starlet's punishing end of year schedule has resulted in the 20-year old being forced to pull out of the Nedbank Golf Challenge with a stomach virus. He won't reappear until the Abu Dhabi Championship from 21-24 January.
McIlroy picked up the illness during the World Cup at Mission hills in China and he was clearly in no fit state to tee it up in Sun City on Thursday. Curiously, it is not the first health scare that McIlroy has suffered this year and it raises questions about this scheduling and his general health.
Chasing the Race to Dubai and world ranking points almost non-stop since the first week in October, the Nedbank Challenge was McIlroy's sixth tournament in a row and his eighth in 10 weeks since the Alfred Dunhill Links Championship.
It is not the first time he has been ill in the last 12 months.
Shortly after he won the Dubai Desert Classic in February, he revealed that he had been suffering from fainting fits and was under doctor’s orders to increase his salt intake.
At the time, McIlroy said: “On Monday I flew over to Leeds and got a blood test and a heart test done as I have the odd faint on occasion but it was just a lack of salt so I need to up my intake a little."
McIlroy felt light-headed as he worked out at the gym and passed out for a few seconds.
According to his father, Gerry, he never takes salt with his food but has been told he can correct the imbalance by taking a specially prepared drink on a daily basis.
McIlroy picked up his stomach virus during the World Cup in China and despite 14-hours sleep on his arrival in Africa, he felt unwell on the range on Tuesday.
He took advantage of a first round weather delay to visit the tournament doctor, who put him on an intravenous drip but bravely insisted on going back out in scorching temperatures.
He posted a one over par 73 and it was no surprise that he withdrew overnight after a second round 76 left him propping up the field.
Food poisoning forced McIlroy to pull out in the second round of the 2006 British Amateur Championship at Prince's Golf Club near Sandwich.
He was already feeling under the weather during a first round 78 at Sandwich but battled on for 12 holes at nearby Prince's before his father Gerry found him in tears.
Doubling as caddie, Gerry said: "I walked ahead on the 12th green to get a yardage and when I turned back I found Rory kneeling on the ground, crying and doubled up in pain.
"He was more angry than anything else because he had put so much into his preparation for this.
"My heart went out to him. I tried to get him to come off the course after three holes but he kept on going.
"The R&A were very concerned about him and I took him back to bed in his hotel and I'm sure he'll be fine soon. But he's really disappointed."
South African Retief Goosen (67) leads the Nedbank Challenge by two shots from Australian Robert Allenby and reigning US Masters champion Angel Cabrera.