(Reuters) - As world number two Dustin Johnson snaps at the metaphorical heels of top dog Jason Day of Australia, the game's leading player has identified the reasons for the American's elevation to the cusp of the global pecking order.

After a sizzling summer, U.S. Open champion Johnson enters the Tour Championship starting in Atlanta on Thursday as the top seed and favorite to clinch the $10 million bonus awarded to the season-long FedEx Cup champion, a points race that roughly correlates with the PGA Tour money list.

The long-hitting Johnson has long been an elite player but has taken his form to another level this year, winning three tournaments in quick succession after improving various aspects of his game, particularly his wedge play.

According to Day, Johnson's focus on his wedges and his use on the range of the Trackman device that tracks the details of every shot have been of paramount importance.

"Every morning he's got a trackman behind him hitting shots, so he knows exactly what his wedges are doing, how far they're going, all that stuff," the Australian world number one told reporters at East Lake Golf Club on Wednesday.

"Three things for him to be successful are driving, wedges and putting ... and that's what he's doing great right now. His wedges have improved, his driving has always been great, and it's even better now he's hitting a cut.

"He used to hit a tiny little draw, but he's a lot more accurate with the cut and he's long, the longest guy out here."

The combination of those three areas of the game has given Johnson a near-perfect recipe for success, said Day.

"You add the length with great driving, you have wedge in your hand more times and once you improve those wedges you have more opportunities for birdies," said the Australian.

"And if you putt half-decently, and he's putting better than half decent, he's going to win a lot of tournaments. It's a formula for success."

Day, fourth in the FedExCup standings even though he has not been in his very best form since cracking his driver in June, will clinch the $10 million jackpot if he wins the Tour Championship on Sunday.

"When you have a lot of confidence and you feel nobody can beat you, it's game over for everyone else," the Australian said, a statement that just four months ago could have applied to himself.

On this occasion, though, Day was referring to Johnson's current state of mind.

(Reporting by Andrew Both in Cary, North Carolina; Editing by Mark Lamport-Stokes)