Australian golfer Jason Day pushes into a tie for second at the halfway mark of the lucrative US PGA Tour Championship.

Jason Day needs a few favours if he is to win the season-long FedEx Cup and a monumental $US10 million bonus but the Queenslander is holding up his end of the bargain sitting tied second halfway through the Tour Championship.

Day once again shook off the loss of his regular caddy and coach Col Swatton, carding a three-under-par second round of 67 at East Lake Golf Club to jump to six under for the tournament, leaving him two shots behind leader and last-start winner Billy Horschel.

Horschel was a shot better on the round with a 66 while world No.1 Rory McIlroy shot 65 to be a looming presence on the boards with Day and current FedEx Cup points leader Chris Kirk (68) at six under.

After starting the event in 10th place on the points list Day must win the tournament, which in itself brings $US1.4 million ($A1.51 million) in prize money, to have a chance at the obscene bonus and also hope Horschel, Kirk and McIlroy stumble over the weekend.

Day needs Kirk (No.1) to finish fifth or worse, Horschel (No.2) must finish in a three-way tie for third or worse, Bubba Watson (No.3) must finish in a three-way tie for second or worse (currently tied 14th) and McIlroy (No.4) must finish T2 or worse.

And he must do all of this while still fighting the lingering affects of thumb and back injuries, and getting his own distances after the loss of an injured Swatton, who missed a complete round for the first time in over 600 competitive rounds of the 26-year-old Day’s professional career.

“I’m still not 100 per cent and, playing with little niggling injuries, it’s definitely not the spot you want to be in but it’s something where you just have to suck it up and play and try and fight for the win,” Day said.

“That’s what it boils down to, if I want it enough. I’ve got to want it more than the guy that’s leading now and the guys that are chasing it.”

For Day to make it, he needs to tighten up from the tee as he is tied 26th in a 29-man field in driving accuracy, hitting just 12 of 28 fairways. On the greens he’s been magic with just 52 putts to be tied first.

“If I can focus and start to turn things around off the tee and give myself a lot more opportunities on the greens, then with the way I’m putting, I feel like I can really push forward,” he said.

“I kind of worked something out on the back nine with my driving, started driving it straighter, so hopefully I can carry that into tomorrow.”

Adam Scott (72) dropped to one over and into a tie for 16th while the tournament is already out of reach for John Senden (+7) and Geoff Ogilvy (+14) as they hold the last two positions.