OK, no such achievement exists, but anything seems possible for the Masters champion in the Peach State.
'Yeah, I'm not sure what it is,' he said. 'You know, for whatever reason, I've had success here.'
Johnson, also the 2004 winner, closed with a 5-under 67 to match Imada (70) at 15-under 273 on the TPC Sugarloaf.
In the playoff on the par-5 18th, Johnson hit his second shot above the pin, then rolled a 60-footer for eagle within 5 inches of the hole. He now had his third PGA TOUR victory, each of them coming in Georgia.
Imada could only offer a congratulatory handshake. His tee shot landed in the left-side rough and his 3-wood failed to clear the water in front of the green.
Laying up was not an option, Imada thought, because with Johnson in the middle of the fairway, there seemed little chance his opponent would make par.
'I don't want to second-guess myself,' Imada said. 'If I laid up, it was going to be a tough shot regardless. The green on 18, front left, is pretty hard. I mean having a 15-footer for birdie, you know, your chances are not good.'
Seeking to become just the third player from Japan to win on the PGA TOUR, Imada lost a critical stroke with a drop that all but ified his next approach, which landed 13 feet from the pin.
For Johnson, scoring conditions the last four days were nothing like those at Augusta National, which endured bitterly cold wind in April when Johnson matched the highest score in Masters history at 1-over 289.
The AT&T, a suburban Atlanta event that moved from the week before the Masters to the warmer temperatures of May, offered a favorite venue for Johnson, the runner-up to Phil Mickelson last year.
Matt Kuchar (70), Camilo Villegas (71) and Troy Matteson (73) tied for third at 12 under, and Chris Tidland (68), Stephen Marino (70) and Bob Estes (70) followed at 11 under.
Mickelson, a week after winning THE PLAYERS Championship, skipped the tournament. Tiger Woods and many of the world's other top golfers did the same.
'This field was great,' Johnson said. 'It didn't have so-called marquee players that everybody knows or the media attaches to, (but) everybody that teed it up this week, for the most part ... is going to be in the top 50, top 30, top 15 players in the world.'
Imada, who began the day with a three-shot lead over Johnson, held his composure after two-putting from 7 feet for par at No. 17. Rather than dwell on disappointment, Imada drove the middle of the fairway before his approach shot flew the green and landed right on top of a sprinkler head 35 yards behind the pin.
The former University of Georgia standout showed some resolve, chipping within 3 feet and tapping in for a birdie that forced a first career playoff for both players.
Villegas, who began the day two strokes behind and in third place, was 13 under after an eagle at the sixth hole and a birdie at the seventh. He struggled with his driver, though, missing four of eight fairways through No. 10 and finishing just 33-for-56 for the tournament.
Johnson had just four bogeys in the tournament, none on the back nine. The Iowa native picked a perfect time for his first birdie at the par-4 15th hole, rolling in a 14-footer that tied Imada.
Since missing the cut at last year's PGA Championship, Johnson has four top-10 finishes and two others in the top 25 while earning money in 11 of 12 events. He withdrew from his second tournament, the FBR Open in Scottsdale, Ariz., because of a wrist injury.
After rolling in a 42-foot putt for a birdie on No. 1, Johnson made three straight birdies to move within one shot of the leaders at the 10th. He stayed 13 under before a birdie at No. 15 forced a two-way tie.
Imada began the day having played the back nine at 10 under, had a two-shot lead with a birdie at No. 12. He missed the green at 14, however, and two-putted for a bogey that dropped him into a tie Johnson.
The only Japanese players to win on the PGA TOUR are Shigeki Maruyama, who won three times from 2001-03, and Isao Aoki, in 1983.
Matteson, who began the final round paired with Imada, had a two-shot lead after he birdied the second and third holes. Following with consecutive bogeys a three-putt at No. 10 essentially ended his chances.
'All day I was either trying to lag it or whack it,' Matteson said. 'I couldn't get in any putting rhythm.'
Johnson has every reason to make plans to Atlanta in September, when East Lake Golf Club hosts the TOUR Championship, but he doesn't want to discuss it with the Memorial in two weeks and U.S. Open looming in mid-June.
'I'm not a firm believer in expectations,' Johnson said. 'I think (if) you get caught up in expecting to do this or that, things go astray. Paramount is the fact that it doesn't matter where you play.'