They had 16 birdies and one eagle between them. Their better-ball score would have been a 59. Beyond the great golf of Rory McIlroy and Tiger Woods that put them prominently on the leaderboard in the BMW Championship, they walked along like they were the best of friends.

A generational rivalry is taking root.

So is a friendship.

McIlroy, nearly flawless with his iron play, birdied the last two holes for an 8-under 64 that gave him a share of the lead Thursday at Crooked Stick with U.S. Open champion Webb Simpson, Indiana native Bo Van Pelt and Graham DeLaet of Canada.

Woods, only sharp when it came to scoring, chipped in from 30 feet on his last hole for a 65.

They traded one magnificent shot after another on a Pete Dye design that was soft and vulnerable, especially on the par-3 sixth hole framed by a pond. McIlroy's tee shot covered the flag and settled 18 feet behind the hole as the gallery erupted in cheers. Woods followed with a tee shot that struck the pin and stopped 5 feet.

Take that, kid.

Both missed the putt, but they made their share of them on a broiling day north of Indianapolis. They chatted endlessly, sometimes Nick Watney joining them, off the tee and behind the green, and at one point Woods playfully shoved McIlroy after an exchange.

When they were done trading birdies, they shared the stage for a television interview, then headed off to the clubhouse for lunch.

"He hits it great, putts it great and top of that, he's just a really nice kid," Woods said of the 23-year-old from Northern Ireland who has endeared himself to Woods and so many others with his game, his manners and the respect he shows.

"The game of golf is in great hands with him, and he's here to stay."

Woods rarely showers anyone with so much praise, and McIlroy was deferent in return. They first played together at Woods' invitational tournament at Sherwood at the end of 2010, and Thursday was the sixth time they have been in the same group this year.

"You're watching a guy your whole life, you're growing up watching him do all these unbelievable things on TV, and then you're stuck there with him," McIlroy said of the first time they played together. "I was a little nervous. I still held my own. But the more I've played with him, obviously the more comfortable I've been, and I think that's showed the last few weeks."

McIlroy was three days removed from his third win of the year — Woods is the only other player with three PGA Tour wins this season — when he won the Deutsche Bank Championship. Woods finished third, two shots behind.

Boy Wonder had every reason to be a little flat because of the short turnaround from the Labor Day finish. But that wasn't the case at the BMW Championship, not with fans lined three-deep down the entire 10th hole to see him and Woods in the same group for the second time in three weeks.

"It definitely gives you a little more of a lift, especially coming off a win and maybe being a little flat," McIlroy said. "You're focused from the get-go, and you want to go out and shoot a good number, and I was able to do that today."

They made it look easy, and Crooked Stick was every bit of that on a broiling afternoon north of Indianapolis.

Because of heavy rains earlier in the week — so fierce on Wednesday that the course was briefly evacuated — players were able to lift, clean and place their golf balls in the short grass before firing at the flags. Really, there was no other option in such soft conditions.

Sixty players in the 70-man field were at par or better. Forty players were in the 60s. All but five holes played under par, and the average score was 69.47.

"I think we all knew it was there for the taking today," said Justin Rose, who opened with a 67 and was tied for 10th.

Vijay Singh had a chance to join the leaders until he drove into the water on the 18th hole, though he escaped with par and was at 65. Luke Donald was in the group at 66. Phil Mickelson was at 69, worth noting because it looked as though he might quadruple bogey on his last hole. Instead, he made birdie.

His second shot from the fairway on the par-5 ninth sailed toward the corporate tents, and Mickelson feared it was out-of-bounds. He hit a provisional that went onto the driving range, which definitely was out-of-bounds. Before he could hit again, Mickelson discovered the first one was in play. Mickelson had a clear enough shot at the green, and he hasn't lost his magic with the short game — his wedge settled 2 feet away for a birdie.

"I got lucky," Mickelson said.

Mickelson played in the group in front of Woods and McIlroy, a dream for any gallery. Even so, cheers could be heard from all ends of Crooked Stick, a testament to how many people were on the course for a Thursday afternoon.

But the biggest crowd followed the two biggest stars at the moment.

"I definitely felt left out for a while," said Watney, the Barclays winner who played with Woods and McIlroy. "But it was fun to watch. Those guys ... they're really good. Rory swings so aggressively, but he never looks uncomfortable. I wish I could have kept up."

Woods and McIlroy got after it from the start. Woods hit into about 10 feet on the opening hole, and McIlroy hit next to 12 feet. McIlroy made his putt, Woods followed that with his birdie putt. There was a two-shot swing for Woods when he hit 8-iron to 4 feet on the 13th hole and McIlroy went long of the green. There was a two-shot swing for McIlroy when he hit 6-iron to 6 feet on the next hole, and Woods came up short and missed his par putt.

There was a stretch in the middle of the round when on just about every hole, one player would hit it close and the other would match him.

"I've always enjoyed playing with Tiger, and every time that we're paired up, we seem to have a good time," McIlroy said.

For Woods, he didn't need the No. 1 player in the world — and the only player besides him in the last half-century to win two majors by at least eight shots — to concentrate on posting a good score. It was the soft ground beneath their feet, the gentle breeze and a 70-man field that meant the greens wouldn't be chewed up by spike marks.

"We just couldn't afford to have a bad start today," he said.