Woods had struggled on Thursdays at events this year - in 14 tournaments, he was an aggregate two over for the first round and 66 under for the other 54 holes - but he put that right in some style with his course record-equalling score.
McIlroy was on the second green when he looked over at Woods, who had just hit wedge to 4 inches for birdie on the seventh hole and was waiting for the green to clear on the par-3 eighth.
The birdies started flowing on the first hole and kept rolling throughout the day.
Some of Woods's shotmaking recalled his great years while the decision to go back to his Scotty Cameron putter with which he won most of his majors worked a treat. "I've been failing a lot, so it would be nice to turn the switch and kind of clutch up".
Woods ended previous year ranked 656 in the world but has risen to 26 on the back of what has been a consistent and largely uninterrupted season after spinal fusion surgery. It's his lowest round in competition since shooting 61 in the second round of the 2013 Bridgestone Invitational. He still hit 14 of 18 greens, but just didn't give himself as many chances.
"Got off to a better start than I have most of the season".
Not so fast, came the response from Xander Schauffele on Friday as he backed up a first round 63 with a second round 64.
"I didn't make any putts".
Woods was posing on his tee shot at the par-3 fifth, the sun glaring into him, and he couldn't figure out immediately where it went.
Rory McIlroy tees off during the first round of the BMW Championship on Thursday. He birdied three of the last four for a 67.
But McIlroy threatened to trump his rival with a round that included a career-best six birdies in a row - before bogeying his 16th and 17th holes.
McIlroy plodded to a 69 to fall four strokes behind, while Woods (70) bogeyed the final two holes to slip five back. "And I didn't capitalize".