Rory McIlroy is 41-under-par in his last 10 competitive rounds, including a 67 on Friday in Valhalla. (Andrew Redington/Getty Images)

Maybe the secret to Rory McIlroy is that even when he swings hard, he’s still. There’s no lashing or lunging in his game. If you set out to sketch the man who’s the new dominant player in the world, you would start with that sense of squared uprightness as he set up over the ball Friday. Neat and shorn-looking in his rain-gray shirt and cap, his feet were evenly splayed, shoulders wide and ruler straight, his forearms strong as truncheons. All of which resolved into such easy, fluent action that everyone else seemed to be slopping in the mud by comparison.

A Nike launch monitor confirms the eye’s impression of the best golf swing you are likely to ever see: McIlroy wallops the ball so hard with his driver that the ball comes off the club 10 mph faster, on average, than his competitors. Yet this is just one reason he is poised to win the PGA Championship at Valhalla, which would be his third straight tournament victory and second major in a month. There’s an understandable temptation to focus on how far McIlroy can hit a ball, especially since it gives hope to all of the other 5-foot-9ers in the world. But that’s just one component; speed and strength don’t wholly explain the incredible scoring run McIlroy is on, a scathing 41 under par in his last 10 competitive rounds, including a 67 on Friday in a downpour.

You don’t do that just by bludgeoning golf courses, especially not one with as much trouble on it as Valhalla, the Jack Nicklaus-designed par 71 that’s full of dank, evil looking lakes and steep swales and tree lines so thick they can make noon feel like midnight. Mention is hardly ever made of this, but McIlroy not only hits it farther, “he hits it higher than most players,” says Nike field rep Rick Nichols, who helped outfit McIlroy with his equipment. That’s as much the secret to his scoring as his distance.

“He really hoists the ball,” Nichols says. “On par-5s, for example, when he’s going in with a long iron, he’s able to hoist a 3-iron or a 4-iron in the air and have it stop on these greens. That’s why he’s able to putt for eagles. He’s able to hoist it and give himself a putt, while others are hitting a wood and running it off the green and they’re chipping.”

Take McIlroy’s eagle Friday on the 542-yard, par-5 18th hole, which helped him move into the lead at 9 under par. It came as he played in a threesome with this year’s other major winners, Masters champion Bubba Watson and U.S. Open winner Martin Kaymer. Watson drove toward a creek bed, launched a 5-wood that went wide of the green, put a wedge to within a few feet and missed a par putt. Kaymer drove into the rough, found a bunker on his second shot and missed a 10-foot birdie putt.

Meanwhile, McIlroy effortlessly launched one of those 350-yard drives dead center, then struck a 4-iron so high the ball seemed to billow to the front of the green. And then he made an uphill 32-footer that rammed into the hole like a billiard shot. Boom. Door slammed. It was a case of strength and finesse meeting aggression and confidence.

“If I’m two ahead going into the weekend here, I’m going to try to get three ahead; and if I’m three ahead, I’m going to try to get four ahead; and if I’m four ahead, I’m going to try to get five ahead,” McIlroy said. “I’m just going to try to keep the pedal down and get as many ahead as possible. That is my mind-set whenever I’m leading the golf tournament.”

A second major victory of the season and fourth overall is not a foregone conclusion for McIlroy, not with a leader board that contained Phil Mickelson, Rickie Fowler and Jim Furyk. But regardless, McIlroy is playing the game with an effortless-seeming facility that others flatly envy, “simply incredible golf,” as Ian Poulter tweeted. He’s in that rare state in which he seems to have full command over the ball — in addition to his distance and height, he’s got range and touch. Just listen to him talk about how he avoided wallowing in the muck of Valhalla in a rain that fell steadily for hours.

“The fairways got very, very wet today, and one thing that I did out there was I tried to sort of clip everything off the top of the grass,” he said. “I wasn’t trying to take a divot. . . . You get just a little bit steep in these conditions, and you can fat it and cover yourself with mud. . . . You have to maybe control your flight a little bit and maybe take spin off some wedges.”

Don’t try that at home. For that matter, don’t try any of the other magic tricks he performs with his Nike Covert 2.0 Tour Driver or his Nike RZN Black ball. One of the things Nichols learned fitting equipment for McIlroy was just how much he is a “feel” player who trusts his own tactile sensations more than mechanics. McIlroy wasn’t content with metrics from robots and launch monitors in choosing his equipment. For instance, his driver spins at about 200 to 300 more rpms than what an equipment expert would consider optimum because McIlroy likes to bend the ball to the left or right. “He felt he needed a little more spin to play the way he wants to play,” Nichols says. “So we didn’t strictly rely on the data. The key is he’s very good at articulating what he’s feeling, and that helps us. He has a keen sense of feel.”

One afternoon as he was testing two clubs, Nichols asked him, “What do you think is the difference?” McIlroy guessed the ball speed and spin before Nichols ever looked at the figures on the launch monitor. “He was able to pinpoint,” Nichols says. “So he was very much in tune. The average golfer would not be able to pick up on it.”

What it all adds up to is a player who has as much promise as we’ve seen in a generation. Which is why Nicklaus earlier this week predicted on ESPN radio that McIlroy could win “15 or 20” major championships before he’s done. “I love his swing, I love his rhythm, I love his moxie,” Nicklaus said. Does it sound premature? It may not by the end of the weekend.

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