The Northern Irishman was in position to end a decade-long hunt for his fifth major on Sunday but threw it away with three bogeys in his final four holes, including two where he missed putts inside of four feet, and lost to Bryson DeChambeau by one stroke.

"Yesterday was a tough day, probably the toughest I've had in my 17 years as a professional golfer," he wrote in a social media post.

"As I reflect on my week, I'll rue a few things over the course of the tournament, mostly the missed putts on 16 and 18 on the final day," he added.

"But, as I always try to do, I'll look at the positives of the week that far outweigh the negatives."

The moment DeChambeau's winning putt dropped in the cup, a shell-shocked McIlroy stormed directly to his courtesy car and left the site of the most agonising loss of his career and fourth runner-up finish in a major.

Despite the gut-wrenching loss, McIlroy, who also finished one stroke adrift of the winner at last year's US Open, said he feels closer than ever to ending a major drought that stretches back to the PGA Championship in August 2014.

"The one word that I would describe my career as is 'resilient'," he said.

"I've shown my resilience over and over again in the last 17 years and I will again."

The four-time major winner was listed in the initial field for this week's Travelers Championship at TPC River Highlands but said he would instead take a break.

"I'm going to take a few weeks away from the game to process everything and build myself back up for my defence of the Genesis Scottish Open and The Open and Royal Troon.

"See you in Scotland."