A year ago, Rory McIlroy strode across the grounds at Congressional Country Club in Bethesda with purpose and pride, head up, chest out, master of everything he saw. After one round of the U.S. Open, he led by three shots. After two, he led by six. All that awaited was a weekend coronation, and what was widely reported as McIlroy’s “first” major championship, because others would surely come.

Friday afternoon, on a green a year and a world away from Congressional, McIlroy removed his cap, mussed his hair, hung his head and shook the hands of his playing partners. Twenty minutes later, he sat on a bench in a nook of the locker room at the Olympic Club, chewing on a sandwich, chewing over what exactly happened here, and packing his clubs.

“It just reminds you, you got to keep working hard,” McIlroy said. “It doesn’t come easy to you all the time.”

McIlroy backed up his opening 77 with a slightly better 73 Friday, but that left him at 10-over par, and thus he will not play the weekend at Olympic.

As Tiger Woods began his afternoon round by seizing the lead in the Open with a birdie at the third hole, McIlroy wasn’t alone in heading home.

England’s Luke Donald, the world’s No. 1 player who competed in McIlroy’s group here, shot 72 Friday and left at 11 over.

“I was a little off,” Donald said. “And that’s going to get you around a U.S. Open course.”

Part of the takeaway from the first two days at Olympic is sure to be the difficulty of the Lake Course, which, midway through the event, appears to be the polar opposite of squishy Congressional, which McIlroy savaged. Woods, too, was setting himself up to be the central story line, because he hasn’t won a major since this event in 2008, and he could be 36 holes from winning his 15th.

McIlroy, though, may leave even the closest observers of his otherworldly game a bit befuddled. His missed cut isn’t just some blip on the radar; it made the fourth time in his past five events in which he has failed to qualify for the weekend. This from the world’s second-ranked player, golf’s next star.

“It hasn’t been the greatest run over the last sort of six weeks, or whatever it is,” McIlroy said. “But as I said, I still see enough good stuff in the rounds that it does give me hope that it’s not very far away.”

Some of that could be true. The U.S. Golf Association, as McIlroy said, set Olympic up “as a real, classic U.S. Open” venue. That means a shot that is even the slightest bit off might be penalized. Donald, who hadn’t missed a cut in his last 24 events, said his errors weren’t major, yet he made 14 bogeys in 36 holes.

“I feel like there’s a fine line between 68 and 78,” said Graeme McDowell, McIlroy’s countryman and the 2010 Open champion whose 72 Friday left him solidly in contention at 1 over at the midway point. “There really is. And it’s just missing a fairway there and missing the green the wrong side here and just sort of not holing out well enough. I mean, honestly, 72 can easily escalate into 78 in a heartbeat.”

Last year, McIlroy described his first two rounds of the Open thusly: “It feels so simple.” In the first two rounds, he made 11 birdies, an eagle and, finally, a double bogey on his 36th hole when he found the pond alongside Congressional’s 18th green. Here, he had no explosions either way, just the drip-drip-drip of 13 bogeys, water torture that couldn’t be offset by only three birdies.

When he reached 10 over after a bogey at No. 5 — his 15th hole of the day — he figured he needed two birdies over his final three holes to get to 8 over and have a chance of making the cut. He got one at the drivable par-4 seventh, and then came to the par-3 eighth, his final hole, thinking he needed one more birdie.

He hit his tee shot nicely, leaving himself 15 feet up a hill. But he ran the birdie putt three feet by.

“I didn’t really take my time over it,” he said, and that putt slipped away from him, some eight feet past the hole. He made the come-backer for one final bogey, and that was it — 131 shots over the first two days a year ago, 150 of them over the first two days here.

“To be honest, overall I don’t feel like I played that badly for the last two days,” he said.

Yet he became the first defending U.S. Open champion to miss the cut the following year since Angel Cabrera in 2008. And he was heading back to his home in Northern Ireland, where he will next appear for the Irish Open. When he tees it up there, he will have considerable questions about his game, and his mind.