The Northern Irish world number four, winner here last year during a storming finish to his 2012 campaign, battled to a six-over-par 77 to end the second round at Conway Farms Golf Club stone last in the elite field of 70.
Only 30 players will advance to the Tour Championship at East Lake after this week's FedExCup play-off event and McIlroy is now projected to wind up 53rd in the points standings, leaving him with a likely four-week break from competition.
"I'm just not scoring well," the 24-year-old said after finishing a staggering 24 strokes off the pace at 13-over 155, having mixed two birdies with six bogeys and a double at the drivable par-four seventh.
"I missed it on the wrong side, I'm missing greens with wedges, and just don't have my scoring hat on. I feel like I'm hitting the ball pretty well, I'm just not scoring."
McIlroy had been encouraged by "glimpses" of good form in the first two play-off events but has since regressed after the US Tour took a week's break following the Deutsche Bank Championship.
"I didn't play any competitive golf, but you come back and you get a card in your hand again, it's a lot different just practising than being out there," said the mop-haired Northern Irishman, who had won two Major titles by the age of 23.
"Just not scoring as well as I need to. I felt really good after the PGA (Championship). When I've actually had a little bit of pressure, that's when I've played my best, so that's a good sign.
"The bad sign is that I'm not in contention too much. It's frustrating, but I'm trying to stay as patient as I can."
McIlroy has endured a frustrating 2013 campaign after moving to the top of the world rankings last year and claiming the order of merit titles on both sides of the Atlantic.
In 15 starts on the PGA Tour this season, he has recorded just five top-10s, including a missed cut at The Open in July.
"Everything sort of came easy last year," said McIlroy. "Now I'm working harder, hitting more balls, spending more time on the range because I'm searching for it (consistent form).
"And that's what's frustrating. But the fact that I'm working hard and I'm not really getting much out of it, if I can keep patient and keep working hard, I'm sure it'll turn around."
Asked how he tried to stay patient, McIlroy replied: "I'm 24. I've got a lot of time in this game still. I've got obviously a few tournaments left this year.
"I'm sort of looking forward to getting to December and drawing a line under the season and start fresh in '14."
As for next week's Tour Championship, that has already been inked out by McIlroy.
"No chance," he smiled. "Yeah, four weeks off. I'll take a little bit of time off and just get my head sharp a little bit, get refreshed and practise and get ready for the last sort of stint of the season.
"It's nice to get a few weeks off, a little bit of a rest and a bit of time to work on my game, and get ready for that Asian trip."
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