But he responded in emphatic fashion and held his nerve to finish at 16-under to win The Players on his 10th try.
But as good as McIlroy's win was, it was a fellow pro who stole the headlines on the day after a costly mistake.
Spanish golfer Jon Rahm held the lead entering the final day's play and sat in a tie for the lead on the 11th hole of the final round.
But after landing in the bunker he went against the advice of his caddie.
Adam Hayes advised Rahm to lay it up, but Rahm shunned the advice and chose to go for the green. He then had to watch his shot land straight in the water.
"I think this will go down in history as the most baffling decision ever struck here at this event," commentator Brandel Chamblee said.
As soon as Rahm decided he was going to go for it you could see what Hayes thought of the decision and ultimately it proved to be advice he should have listened too.
The bizarre choice from Rahm saw him end with a bogey on the 11th hole and it clearly affected his mindset as he tumbled down the leaderboard.
Known for having a temper, the 24-year-old never settled and went on to bogey the 15th before a double-bogey on 17 saw him finish in a tie for 12th place.
Of course it's impossible to know if he would've won the trophy had he taken his caddie's advice, but it is clear the decision to shun him began the downward spiral.
The resulting fall saw Rahm walk away with a pay cheque of $356,000. A far, far cry from the monster pay pack McIlroy was handed.
McIlroy's win earns him a staggering $3.1 million, meaning Rahm's choice to not listen to the experience of his caddie cost him $2.8 million. Ouch.
Rahm did his best Tin Cup impersonation as he threw away a chance to claim the trophy, guaranteed next time he'll listen to his caddies advice.
- news.com.au/AP
