Casey was down in the dumps after an opening 81 that led to an early exit in the 2019 version won by Tiger Woods, but he’s back feeling in love with the Georgia venue after opening with a bogey-free seven-under-par 65 on this occasion.
That earned him a two-shot over American duo Webb Simpson and Xander Schauffele, as well as another home man, Justin Thomas, who was among a large group of players unable to finish their first circuit following a three-hour delay in the morning due to bad weather.
Defending champion Tiger Woods is also off to a strong start after a 68, which was his first bogey-free opening round in this event, while 2018 champion Patrick Reed and 2010 Open winner Louis Oosthuizen signed for the same course.
But an abbreviated first day in the rescheduled event, having been postponed in April due to COVID-19, belonged to Casey as he carded an eagle and five birdies to match his lowest score in this event.
“It was a great round,” said the 43-year-old, who recorded his best finish in this event when sharing fourth spot in 2016. “It was just very, very solid golf.
“I did the right things when I needed to, and, to be honest, you rarely walk off this golf course going, ‘it could have been two or three better’, but it kind of felt that way. I don't want to be greedy. I'm very, very happy with my 65.”
In golf’s first major after the lockdown, Casey finished second behind Collin Morikawa in the US PGA Championship at Harding Park in San Francisco in August.
He then gave another good account of himself with a top-20 finish behind Bryson DeChambeau in the US Open at Winged Foot in September, but this week is the one he’s had circled on his calendar.
“This is something I've looked forward to,” said Casey, who is based in the US, where he has won three times on the PGA Tour. “I was vocal earlier in the year at Harding Park about not enjoying golf in a pandemic. I'm acutely aware I'm in a very fortuitous position.
"I still get to be a professional golfer and play championship golf, but I didn't know how the fanless experience would be. And, so far, I've not enjoyed it, and I've lacked that feeling of energy. I've had nothing or very little to draw from being out playing tournament golf.
“The Masters, though, it still has a buzz to it. There's an energy and a little bit of a vibe. Yes, it's clearly a lot less than what we are used to, but there's something about this place that I still felt excited to be here.”Where does that buzz come from? “I guess the history,” he added. “I mean, the golf course itself is part of it. The history of this championship, this tournament.
“So many people like myself are just excited to play this. You know, this is a treat. It always has been and always will be a real treat.
“There's many great golfers who are not here this week because they are not high enough in the rankings and they are envious of every single player in the field. It's not lost on me.“
Adding to a good day for English players, Lee Westwood marked his return to the event after being absent since 2017 with an equally-impressive 68, having raced to the turn in five-under before dropping his only shot of the day at the par-3 12th.
“It was nice to come back,” said the 47-year-old, who finished runner-up here in both 2010 and 2016. “I’ve obviously played well here in the past, but have missed the last two and nobody likes sitting at home watching this tournament when there is a chance you could be playing in it.
“It is good to be back and it is nice to start off with a good first round and play myself into the tournament.
“I played well. I missed a couple of putts, one from six feet on four and 12 feet straight up the hill on the first. I gave myself a lot of chances, I was really close to the hole a lot.
“I played well on the back nine without getting a few breaks and carrying on from five-under and shooting seven, eight, nine-under. I’ve been playing well recently and I continued to do so today.”
The former world No 1 has recorded six top-10 finishes in total here, but admitted: “I found it really tough at the start. The first few years playing here it was tough to see a good score round this golf course.
“I played well, but I thought 71-72 was a really good score. Then I started to get it and realise where you needed to hit it and where to keep away from and I’ve gradually built up my game plan where I go out there now and see a score.”
Simpson, the 2012 US Open champion, eagled the second before making a good par save at his closing hole, while Schauffele’s strong start was built on the back of a total of seven birdies, including four on a bogey-free back nine.
US Open champion Bryson DeChambeau recovered from an ugly double-bogey 7 at the 13th - his fourth hole to card a 70, which was matched by 62-year-old Larry Mize as the 1987 winner produced one of the rounds of the day.World No 1 Dustin Johnson and career grand slam-chasing Rory McIlroy are among the players still to finish their opening rounds, sitting on three-under and level-par respectively after nine holes.