Casey shot a bogey-free 65 with five birdies and an eagle, putting him two strokes ahead of Americans Xander Schauffele, Webb Simpson and Justin Thomas, who is 10 holes through his opening round.

The 43-year-old Englishman missed the cut at the 2019 Masters and tied for second at the 2020 US PGA Championship.

Last year, Casey shot 86 and 82 to badly miss the cut. But he turned things around in his return to Augusta National, which was delayed for seven months by the coronavirus pandemic.

Starting on the back side, Casey made five birdies and rolled in an eagle at the par-5 2nd hole to match his lowest score ever at the Masters.

Casey has never won a major title, but he's usually part of the mix at Augusta. He's had five top-10 finishes, with his best showing being a tie for fourth in 2016.

"I've not played particularly great golf since the whole pandemic hit," Casey said. "I put in a lot of hard work in a short amount of time and it paid off today with the score I shot."

"There is a vibe that Augusta National has. The aura – there's something you can't measure that just adds to the excitement." – Paul Casey

Augusta National isn't allowing fans, but Casey said he still felt an extra bit of excitement.

"There is a vibe that Augusta National has," he said. "The aura – there's something you can't measure that just adds to the excitement."

Defending champion Tiger Woods finished his first round bogey-free, with four birdies in his first bogey-free round at a major tournament since the 2009 US PGA Championship.

Woods is now tied for fifth at four-under par.

The 15-time major winner's signature fist pump was on display as he played confident and injury-free golf with birdies on the 1st, 13th, 15th and 16th holes.

Meanwhile a late string of birdies put 1987 Masters champion Larry Mize into the red numbers.

The 62-year-old shot an opening two-under 70 to break par for the first time in 11 years at Augusta.

Mize famously won the 1987 Masters in a playoff when he holed a 140-foot chip on the 11th hole to beat Greg Norman.