The long-hitting American played superb golf in difficult scoring conditions at a rainy East Lake on Saturday, firing a three-under-par 67 to end the third round at seven-under 203, alone in second place, four strokes behind leader Henrik Stenson.
His round included four birdies at the long and challenging layout and he signed off with a stunning 30-foot par putt at the last.
"I played really good today, just really solid all day long," Johnson told reporters.
"Made a lot of good shots and had a lot of looks at birdies. Just one bogey today, and it was playing pretty tough out there, so I'm very pleased with that."
Johnson, a seven-times winner on the PGA Tour, was the last man to qualify for the elite field of 30 players after finishing joint 62nd out of 70 at last week's BMW Championship in Chicago.
"Definitely a lot more excited," he said of his mood change since his poor finish in the penultimate FedExCup playoff event. "Leaving Chicago, I was just frustrated that I was struggling. I like the golf course. I just really struggled.
"I struggled with the putter more than anything last week. I three-putted like 10 times, just wasn't holing anything.
"After I got in on Monday, I just came out and did a lot of work with the putter and the golf swing with (coach) Butch (Harmon)."
His work with Harmon reaped instant reward as he opened with successive scores of 68 at East Lake and went on a 39-hole stretch without a bogey until he made his only error in the third round at the par-four 14th.
"You got to play good," Johnson said. "I'm not driving a lot. When I did miss the fairway, it was just off. It was on a hole where I could get it on the green from the rough.
"It was just a good solid stretch of golf. I think I've played about the same from when I teed off (on Thursday) until now. I'm just hitting the ball solid, hitting it where I'm looking.
"If I can keep driving it straight, then I'm going to give him (Stenson) a run tomorrow."