Day, making the most of rain-softened conditions at Firestone Country Club, fired a sizzling seven-under-par 63 to take control in the elite World Golf Championships (WGC) event.

The 23-year-old rolled in an 18-foot birdie putt at the par-four ninth, his final hole, for a three-stroke advantage over Americans DA Points, Stewart Cink and Brandt Snedeker, South African Rory Sabbatini and Dane Thomas Born.

British world number two Lee Westwood opened with a 67 to end the opening round level with Americans Phil Mickelson, Jonathan Byrd and Keegan Bradley.

Woods, a seven-times champion at Firestone who is returning to competition after a 12-week absence due to leg injuries, was level for the day after parring his first six holes.

Day, one of the hottest players on the PGA Tour this season with seven top 10s in 15 starts, was delighted with the quality of his ball-striking in hot and humid conditions.

“I hit driver well and hit a lot of good quality iron shots,” the Australian told reporters. “I didn’t stomp it all day, but I hit it to a good 15 to 20 feet all day.

“I hit a lot of good quality putts and it felt like it was a boring kind of a game. It was down the middle, on the green and every two or three holes was a birdie which was nice.”

Long touted as one of the game’s most exciting prospects, Day won his first PGA Tour title at last year’s Byron Nelson Championship and he relishes playing among the world’s elite.

“I’ve always wanted to play on the big stage, and I’m finally here,” he said. “Obviously I just want to keep the year going in the right direction. I don’t want to go backwards.”

Westwood, who has recently been working with American guru Dave Stockton on his putting, was elated after a solid display on Firestone’s greens.

“I played well and rolled it nicely on the greens, so I’m pleased with everything,” the Englishman said after recording five birdies and two bogeys.

“A 67 is never anything to complain about around this golf course, even when there’s not much wind and it’s playing soft. It has its trickeries out there.”

British world number one Luke Donald and US Open champion Rory McIlroy of Northern Ireland opened with matching 68s.

Donald’s tidy round featured two birdies while McIlroy recovered from two early bogeys with two birdies and an eagle at the par-five second.

“I didn’t get off to the best of starts ... but got it back pretty nicely,” said the 22-year-old McIlroy, who won his first major title by a staggering eight shots at the US Open in June.

“I played pretty solid on the way in, and had a couple of nice up-and-downs. It was a decent opening round. Still got a little bit to work on, but 68 is not a bad start.”