By Thursday evening, someone needed to take this U.S. Open, grab it by the shoulders, and shake some sense into it. It wasn’t going to be the three top-ranked players in the world, who went off together in the morning cool and drizzle, then stumbled home, each with only a long-range view of even par. It certainly wasn’t going to be Phil Mickelson, whose all-over-the-place round must be cast in a funhouse mirror before it has a chance of being understood.

And it wasn’t going to be Congressional Country Club’s Blue Course itself, either, because the exhaustingly long track played easily in spots, downright viciously in others, confusing to the core.

So after 6 p.m., when rain started to fall again, up came Rory McIlroy, the young man from Northern Ireland known for his boundless talent, his exuberant spirit — and, unfortunately, his collapse at the Masters. His response, both to a hectic opening day at the U.S. Open and any demons he still may carry: a bogey-free 6-under-par 65 that sets him apart from a leader board crowded with former major winners and surprises alike.

“It’s not going to be that easy every day,” McIlroy said. “I know that. I think everyone else knows that.”

The other folks who found Congressional’s 7,574-yard layout at all easy: Charl Schwartzel of South Africa, the reigning Masters champion, and Y.E. Yang of South Korea, the 2009 PGA champion, who each shot 68. The group of six players at 69 included 2010 British Open winner Louis Oosthuizen, Schwartzel’s countryman, and Spaniard Sergio Garcia, whose decade-long-plus quest for his first major continues here.

The diversity on that leader board fits both a U.S. Open and the state of the world game right now. But there is no better way to demonstrate all that happened here Thursday — a day that began at 7 a.m. and lasted until nearly 8 p.m. — than to look at McIlroy, seeking his first major, and Mickelson, who already owns four but is after his first U.S. Open.

They went off in the same star-studded group. They played the course completely differently from the start. McIlroy’s opening tee shot at the par-3 10th: safely on the green, one of 17 greens he hit on the day, best in the field. Mickelson’s opening tee shot, a moment later on the same hole: dumped into the water, leading to an opening double bogey.

“It was pretty much stress-free golf,” McIlroy said.

McIlroy might have been alone in that sentiment.

“I hit it horrific today,” Mickelson said.

Mickelson was definitely not alone in that one, but he was singular in the style in which he delivered those horrors. He managed to hit all of five fairways, and made some bizarre decisions along the way. At the massive 494-yard par-4 11th, he hit 2-iron off the tee, then 3-wood out of the second cut of rough. Somehow he made par. At the eighth, he carried his tee shot so far left, it ended up in a greenside bunker — at the adjacent fifth. He finished with a 3-over 74 in which he took the most meandering tour of Congressional possible.

“This could have been a day that’s easily in the 80s,” Mickelson said, “and somehow I was able to get myself around and be only 3 over.”

Though Mickelson and McIlroy — joined by Dustin Johnson — made up the group that drew the largest galleries in the afternoon, the morning opened with the top three players in the world playing together: Luke Donald, Lee Westwood and Martin Kaymer. Their scores: 74, 75, 74, respectively. Mickelson was joined at 74 by Ryo Ishikawa, Jim Furyk, Justin Rose, Rickie Fowler and Hunter Mahan. Ian Poulter and Johnson joined Westwood with a 75. All on a day that began with showers, saw some sun in the middle, and finished with rain again.

“I thought the golf course was set up great today if you played well,” said Westwood, who didn’t. “I’m quite surprised nobody’s gone out this morning and shot 66.”

In the afternoon, McIlroy did him one better. He has, in the past two months, been forced to discuss his final-round 80 at Augusta National, in which he turned a four-shot lead into a deflating defeat. He has consistently said that he analyzed the problems with that round — “just being too tentative,” he said — over about a week, and moved on. And while, at 22, he hasn’t yet shown he knows how to close out one a major championship, he certainly knows how to start one. His last year has included an opening 63 at the British Open at St. Andrews, a first-round 65 at Augusta, and now this.

When McIlroy played the fifth hole — his 14th of the day — he even thought the most tempting of thoughts. He stood at 5 under. Birdies on four of the last five would have given him a 62, a new record for a major.

“It did slip into my mind,” he said.

And why not? While so many players gritted teeth just to survive, McIlroy’s one bit of pressing came when he missed the fairway at the 14th and had to hole a 15-footer for par. He buried it, the longest putt he hit all day.

“I didn’t do much wrong,” he said.

“The game’s easy when you hit it straight and make every putt,” Mickelson said. “It’s a wonderful game. No course is too tough when you hit it like that.”

Now, then, the tough part. Thursday, McIlroy restored order at Congressional by putting a prominent name atop the board. He has done that before. What comes next?

“There’s 54 more holes left to play,” McIlroy said. “I know that more than anyone this year. There’s a long way to go.”