The memory of his final round meltdown last year, when he blew a four-shot lead, hung over the build-up to the tournament with many curious to see if he could better handle a Sunday showdown this time around.
The Northern Irishman, the defending US Open champion was well-poised for a weekend push after his 69 on Friday to follow an opening 71.
But Saturday's five-over 77 ended any realistic hopes for the 22-year-old to contend and, having set himself a target of a top-10 finish on Sunday, his lowly placing was a real let-down.
"It was a disappointing weekend, just one of those things," McIlroy said.
"I played pretty well over the first couple days and then just came out on Saturday and really just didn't have it that front nine and that sort of killed me for the rest of the tournament. It was just one of those things.
"But I'll come back next year and try my best again."
Some in the media had billed the tournament as a two-man race between McIlroy and Tiger Woods but in the end the only accuracy in that prediction was that there was little to choose between the pair after they finished level at five-over 293.
McIlroy struggled all week with the par-four first hole, making two double-bogeys and a bogey there, but it was his overall play that lacked the sparkle he has shown since clinching the US Open in such fine style at Congressional.
"I got off to a bad start and just couldn't really recover from that," he said. "I felt like coming into the weekend I had a chance and sort of blew up the first nine holes on Saturday and it wasn't great.
"I was just trying to recover some today, but I didn't really have my best game."
The Northern Irishman does not plan to over-react to one setback, saying there was not one single area of his game that let him down.
"It was just sort of a combination," McIlroy added. "I actually felt like I played okay, just a couple yards off here and there and missed the slopes and missed the greens in the wrong spots. If you do that here, then it's very difficult."
Now McIlroy's attention will turn to the defence of his US Open title at the Olympic Club in San Francisco in June.
"I'll take a couple weeks off, reflect and think about anything that I tried to do that I didn't do so well and try and put it right and just try and get back at it and prepare for the US Open," he said.
"That's one I really do try to get myself up for. Just got to go out to San Francisco and try to get another major."