Scott, with Woods’ former caddie Steve Williams now on his bag permanently, played the par-70 Firestone layout without a bogey, firing eight birdies to take the lead in the elite World Golf Championships event.
Day, who tied for second with Scott at the Masters in April, played in the morning when the course was at its most receptive and had seven birdies in his bogey-free round.
American Nick Watney, who won the World Golf Championships event at Doral this year, was third with a 65 despite a bogey at the final hole.
He was followed by a group of nine players on 66: South Africa’s Rory Sabbatini, Denmark’s Thomas Bjorn, Scotland’s Martin Laird, Korea’s Kyung-tae Kim, Spain’s Pablo Larrazabal and Americans Stewart Cink, Brandt Snedeker, D.A. Points and Ryan Moore.
But the player drawing the most attention was undeniably Woods, who teed it up in competition for the first time since limping out of the Players Championship on May 12.
Woods admitted he was nervous, but showed no sign that he was troubled by the left knee strain and Achilles tendon injury that he first suffered in April at the Masters.
He carded a two-under 68 that put him in a group of 14 players sharing 18th place.
“I hadn’t really gone at it yet until basically today, just kind of plodding away, just kind of hitting shots,” Woods said. “Today was just, let’s go, let’s go play, just put everything aside and let’s go give it a go and try to post a low number.”
Woods, who played his last complete round at the Masters in April, posted his lowest opening round of the year and said he would be even better prepared mentally on Friday.
“I’ve got the competitive feel now,” he said. “I know what it feels like to get into the flow of the round, the rhythm of playing and walking, and just the flow of playing tournament golf, which is way different than zipping around in shorts and a cart.”
Scott’s round matched his career-low, but he said his new caddie wasn’t too impressed.
Williams carried Woods’ clubs for all of his seven victories at Firestone. That included his 2000 triumph, when he had a record total of 259 to win by 11 shots.
“He didn’t think it was a big deal to shoot 62,” Scott noted. “It was normal.”
Day went out in the overcast morning conditions and grabbed the clubhouse lead on 63, capping his round with a birdie.
“It felt like it was a boring kind of a game,” Day said. “It was down the middle, on the green, and every two or three holes was a birdie, which was nice.”
Scott, starting in the afternoon, saw the low scores and decided on an aggressive strategy. His first birdie came at the par-five second hole. After birdies at six, eight and 10, he added three in a row from the 13th and one more for good measure at 17.
“I just feel like I need to get myself in these things from Thursday, show up and go, not show up and see how you get on the first nine,” Scott said.
“I feel like that’s a good way for me to go because I’m hitting the ball well, and I feel really confident on the greens. It was green light and just attack.”