McIlroy, fresh off his win at the Deutsche Bank Championship on Monday, mixed an eagle, seven birdies and a lone bogey for an eight-under 64 at Crooked Stick Golf Club that put him in a tie for the lead with Americans Webb Simpson and Bo Van Pelt and Canadian Graham DeLaet.
Van Pelt, who failed to make the US Ryder Cup team this week, may have had captain Davis Love III rethinking his picks after a bogey-free round while Simpson, an automatic selection, was equally impressive, particularly on the back nine stringing together four consecutive birdies from the 14th.
DeLaet, still seeking a US PGA Tour win, was the unknown on a leaderboard packed with former and current world number ones, multiple Major winners and Ryder Cup members.
But the unheralded Canadian certainly looked like he belonged, mixing seven birdies and an eagle against one bogey for his 64.
With the suspense of Ryder Cup selections over, the focus is back on the FedEx play-offs this week and there is plenty at stake with the elite field of 70 players vying for one of 30 spots in the September 20-23 Tour Championship finale in Atlanta where the overall points winner gets a $10 million bonus.
The only players with three US PGA Tour wins this season, Woods and McIlroy were paired together for the second time in three weeks.
Joined by American Nick Watney, the trio garnered most of the attention from spectators on a sweltering hot day in the American Midwest as Woods and McIlroy went toe-to-toe producing a scintillating display of quality shot making.
After the two rivals birdied their opening hole it was clear the massive gallery was in for a special treat.
No one enjoyed the round more than Woods and McIlroy, who spent much of the afternoon laughing and chatting before leaving the course singing each other's praises.
"This is the next generation of guys coming out," gushed Woods to reporters. "He (McIlroy) hits it great, putts it great and on top of that he just a really nice kid.
"The game of golf is in great hands with him and he's here to stay."
For McIlroy the feeling was mutual.
"I've always enjoyed playing with Tiger, every time we are paired together we seem to have a good time," said the Northern Irishman.
"You're watching a guy your whole life, you're growing up watching him do all those unbelievable things on TV and then you are stuck in there with him."
As the US PGA Tour season reaches a climax both McIlroy and Woods appear to be hitting on all cylinders.
McIlroy, who has won two of his last three starts, arrived at the US PGA Tour's penultimate FedExCup play-off event leading the points standings.
Woods' play in the opening round offered more proof that the world number three is close to recapturing his best form.
A year ago, Woods, struggling with injuries, fallout from his divorce and a swing overhaul failed to even qualify for the lucrative season-ending series.
But the former-world number one, who passed $100 million in career earnings last week, is in the hunt for another big payday sitting third in the standings and a shot at the big bonus.
"I was scoring, I wasn't playing particularly well," said Woods, summing up his round. "Rory on the other hand played beautiful today.
"Every single part of his game was working.
"I was very fortunate to post the number I shot."
Woods was joined on seven-under by Fijian Vijay Singh while Briton Luke Donald and Americans Ryan Palmer and Ryan Moore are on six-under 66s.
Briton Justin Rose got the defence of his title, won last year at Cog Hill near Chicago, closed with three birdies for five-under 67 to sit three off the pace.