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Everything seemed effortless for Rory McIlroy last year in the U.S. Open.

He opened with a 65, then kept cruising at rain-softened Congressional en route to an eight-stroke win.

This year at The Olympic Club, McIlroy might not even be around for the weekend unless he plays better than he did Thursday. He shot a 7-over 77 and was 11 strokes behind first-round leader Michael Thompson.

"I just too many times was in the wrong position off the tee or with my second shot and it makes it very difficult," McIlroy said. "When you're trying to play catch up on this golf course, it's very hard ... you have to be so precise. Anything just a little off and it really punishes you."

Through 16 holes McIlroy had already missed 10 greens — the same number he missed in four rounds at Congressional when he shot 16 under to set a record with the lowest score in championship history.

He missed the last two greens as well and finished bogey-bogey.

"Seven-over is a big hole for any player," 2010 U.S. Open champ Graeme McDowell said when asked about his Northern Ireland countryman. "Rory McIlroy's a pretty good player though, so if anybody can come back from it, he can. But this golf course doesn't really offer up many 64s."

Even on the reachable par-5 17th, McIlroy walked away with a bogey.

Credit goes to Olympic's tight, twisting fairways and rock-hard greens — a stark contrast to Congressional.

But there also was no energy to feed off of in the marquee afternoon grouping, which featured top-ranked Luke Donald, No. 2 McIlroy and No. 3 Lee Westwood.

Donald shot a 9-over 79, and Westwood was 4 over through the first six holes before steadying himself and finishing at 73.

Donald insisted there wasn't much time for chit-chat to boost one other.

"The U.S. Open demands your full attention, and obviously Lee had a good back nine, but Rory and I both struggled," Donald said.

McIlroy was so deep in the rough on No. 12 his next shot came out sideways, and led to another bogey.

On 13, he threw a tired fist-pump when he finally hit the green and sank a birdie putt.

But he couldn't keep it going.

He mashed a 3-wood on the next tee, leaving him just 79 yards to the green on the 419-yard par 4. But he missed the green left with a wedge and had to settle for par.

On the par-3 15th, McIlroy's tee shot came up short and disappeared into the deep rough. He couldn't get any closer than 20 feet with his chip, and missed the par putt.

The 77 was the third-highest opening-round score for a defending champion dating to 2001 — with Angel Cabrera (2008) and Retief Goosen (2002) both posting 79s.

"There's a fine line on this golf course between (a) 68 and 78 really," McDowell said. "There really is. It's fine lines. And the key, one of the big keys this week is to get off to a nice start and don't let the place beat you up too early."

McIlroy did just that, opening with a bogey then posting three more on the front nine and four on the back.

It was a far cry from a year ago when, after his runaway victory, some were suggesting McIlroy might be the guy to challenge Jack Nicklaus' benchmark of 18 majors.

McIlroy looked better throwing out the first pitch at a San Francisco Giants game on Tuesday than he did negotiating Olympic on Thursday.

He insisted he wasn't feeling the pressure as defending champion.

"I tried to approach it like any other tournament I play," said McIlroy, who initially declined all interview requests before offering a few quotes 20 minutes after his round ended. "I tried to go out there and shoot the best score I could. And today wasn't my greatest day, but hopefully I can come out tomorrow morning and try and shoot a good one and at least try to be here for the weekend."

McDowell expected as much.

"He'll be coming out with guns blazing tomorrow trying to get himself back in the mix," McDowell said.

McIlroy knows it won't be easy.

"I've got to hit it in the fairway for a start," he said. "And from the fairway, I've got to hit it on to the green. You just keep it simple and try to hit fairways and try to hit greens and not be too greedy."