The American, who missed the first two FedExCup Playoffs events, said he had been "battling for my life" in Houston Methodist Hospital in Texas, after returning to action with a two-over-par 72 in the first round of the Tour Championship.

"I think I was in there for five or six days. I don't know exactly how long," the Masters champion told reporters at East Lake. "I don't remember the exact timeframe I was actually in the hospital, but it felt like an eternity.

"First couple days they were sitting there telling me that make sure you text your family quite a bit, talk to your family, because you just don't know. I mean, this is not good. We're not in a good spot right now.

"With how the hospitals are these days because of COVID and everything that's going on, it doesn't matter what's going on. They won't allow people in there, so it's only you in there.

FedExCup leader Patrick Cantlay maintained his two shot lead at the Tour Championship on Thursday. PHOTO: Kevin C. Cox/Getty Images.

"So I'm sitting there and those first two days the only thing that was going through my mind is I'm not going to be able to tell my kids goodbye. I'm not going to be able to tell them I love them. I'm not going to be able to tell my wife that I love her and give her a hug.

"It definitely puts you in a dark space when you're in there, especially those first two days. But I'm so happy to have such an amazing team and such amazing doctors that were working with me to get me through it and to get me working in the right direction on the way up.

"And to think that I'm able to be here and play, I really felt okay. I mean, it's a little frustrating not having the speed, not being able to hit the shots and really feel certain things quite yet, but I took a ton of time off.

"I mean, I was battling for my life. I was in the hospital. And the good thing is now I can hit the ground running hopefully."

Reed admitted he would not be playing in Atlanta if not for the need to impress Ryder Cup captain Steve Stricker and earn one of the six wild cards which Stricker will name on Sunday.

But Patrick Cantlay is certain to be at Whistling Straits after his victory in the BMW Championship secured the final automatic qualifying place and also took him top of the FedExCup standings.

That meant Cantlay started the Tour Championship with a two-shot lead on 10-under-par, a lead he maintained thanks to an opening 67 on Thursday.

World No.1 Jon Rahm replaced Tony Finau as Cantlay's nearest rival, the U.S. Open champion playing his last seven holes in four-under-par in his 65, while Finau fell seven shots off the pace with a 72.

Bryson DeChambeau and Harris English were five off the lead on eight-under, English making a hole-in-one on the 15th and birdies on the next two holes in his 66.

Australia's Cam Smith, who started at five-under, is at seven-under after shooting a 68. He is tied fifth with Viktor Hovland, six behind Cantlay.