As Rory McIlroy stepped to his first hole of the U.S. Open, he faced a shot that some consider so difficult it constitutes an unfair challenge to start such a vital event. Half the field started its Thursday round on the 10th hole. On Friday, the other half has that dubious treat, facing a 218-yard mid-iron over water to a false-front green with sand behind it.

“I hit a great shot to start the day, and it really got the round going,” said the 22-year-old from Northern Ireland who was about to unleash one of the purer ball-striking rounds in the annals of major tournament golf. “I’ll be a lot more at ease tomorrow morning.”

Heaven help Congressional Country Club if he tops his 65 in this first round.

McIlroy, whose last day at a major championship was an utterly miserable 80 at the Masters, striped a 5-iron shot that covered the flag and ended up 10 feet past the hole. Then, he duplicated that swing, that flowing tempo, all afternoon, hitting 17 greens in regulation during a 6-under-par clinic that McIlroy called “a simple 65.”

Well, he would know. Last year at the British Open, he began with a 63. At Augusta in April, he started with 65. This appears to be an otherworldly habit for the supple lad who admitted that with five holes to play, the thought crossed his mind that he might shoot “the lowest round in the history of the majors” with a 62.

At most Opens, there is a brutal sequence of holes that quickly identifies which players have arrived at golf’s toughest event with their games in crisp shape and the proper blank-brained serenity, ready to contend. But those holes are seldom, if ever, the very first two you must play to begin the Open.

But that’s the hellish challenge this week, as the two most terrifying consecutive holes on the course are the treacherous 218-yard par-3 10th over water and the vicious 494-yard, par-4 11th with water down the right, a ribbon-thin fairway and danger everywhere.

McIlroy, Phil Mickelson and Dustin Johnson — this event’s glamour threesome, followed by the biggest gallery of the day by far — arrived at that 10th tee at 1:36 p.m., knowing that big names such as Ernie Els, Nick Watney and Ryo Ishikawa had already blown up with double bogeys or worse on at least one of those two holes, leaving their composure shattered and their chances damaged in an instant. For all three men, answers that may define their fate here this week came instantly.

McIlroy “prepared” for this Open by going to Haiti on a UNICEF mission. He felt it cleared his mind, gave him a sense of gratitude and, to say the least, made playing golf seem like a “test” that a fellow ought to be able to face. On his cellphone, his screen saver was a picture of the presidential palace “where the dome is just hanging off.”

After his discombobulated final-round 80 at the Masters, blowing a three-shot, 54-hole lead, McIlroy also sought out his mentor in recent years, Jack Nicklaus, at the Memorial tournament.

“We had a laugh and a bit of a joke about it,” McIlroy said. “He said he would kick my backside. . . . He didn’t [actually] threaten to beat me up. I think I can take him.”

McIlroy’s easy confidence with Nicklaus, and Jack’s affection for him, which extends back through previous lunch talks on golf and life strategy, shows the place that awaits the Northern Ireland prodigy.

“He said that I shouldn’t be concerned with other people putting pressure on me,” McIlroy said. “I should be putting it on myself. That’s what he did. He said, ‘I’m expecting big things of you.’ It’s a nice pressure to have.”

Playing in the same group with McIlroy may soon be considered an unhealthy form of pressure for even the game’s best or strongest players, like his first-round partners.

Johnson came apart at the 11th with a triple-bogey 7 that makes us (and him) doubt that this is his week or Congressional his place. His sliced drive, right-of-right, was ridiculously unplayable. His mid-iron approach was dead in the greenside pond as soon as it left his club. By the time he stepped on the green, he had used a sleeve of golf balls and needed all the fingers on one hand to keep his score.

Mickelson might have learned another of golf’s endless hard lessons with his very first shot of this Open: Never say you hate a golf hole. They not only have tees and greens; they have ears. The ears, of course, are actually your own. You hear yourself expressing your disdain for the miserable ill-begotten abomination. But you know what’s really in your voice: It’s fear. It’s not the hole that you think is unfair; you just know you can’t play it.

Earlier this week, Phil slandered No. 10.

“The 18th is a brilliantly designed golf hole; I think 10 is the exact opposite,” he volunteered. “When I play that hole, 3 is a great score. I’ll take 3 every day, and if I happen to make a 4, so be it. But you’ve got to take the front [water] out of play. So you have to miss that hole long.”

So, where did Phil hit his first shot of the Open? Short. His sloppy iron shot never had a choice but death at sea. “Happy birthday, Phil. Best wishes, The 10th.”

Thanks to McIlroy’s brilliance, an ugly undertone was erased from this day. The USGA tries to identify the best player in the world. On Thursday, it succeeded in identifying a typical Booz Allen Kemper Open field.

Meantime, the Nos. 1-2-3 ranked players — Luke Donald, Lee Westwood and Martin Kaymer — shot 74, 75 and 74 as their gallery dwindled to near zero.

But by evening, along came McIlroy with his gleaming 65. Suddenly, all’s right with this U.S. Open and then some.