Jason Day's US PGA Tour season has come to a sad and abrupt halt, with the world No.1 forced to give up the fight for the championship and lucrative FedEx Cup with a recurring back injury.
Day withdrew through seven and a half holes of round two at Atlanta's East Lake Golf Club on Friday, giving up a chance to claim $US11.53 million and likely his shot at Player of the Year.
He was just three shots behind the lead but in the midst of making a mess of the eighth hole when he decided to pull the pin as back spasms continued to plague him.
The Queenslander suffered an annulus ligament tear in a disc in his back at the BMW Championship less than two weeks ago but attempted to chase the season-long title this week.
While he sat just one shot off the lead after the first round, the complaint flared up once more, forcing a mostly precautionary early exit.
"Just not enough time to get it rested," Day told PGATOUR.com as he left.
His management team released a short statement soon after.
"Jason has a strained ligament in his lower right back with muscle spasm," it read.
"He withdrew as a precautionary measure. Jason should be fine with some rest after a long break in the off-season."
Day is due to return to the Australian summer of golf in November for the first time since 2013 but this latest setback could throw a cloud over his participation in the Australian Open and World Cup of Golf.
The Australian Open is set for Royal Sydney on November 17-20 with the World Cup being played at Kingston Heath on November 24-27.
World No.2 Dustin Johnson continued his impressive form and now appears a certainty to beat Day to Player of the Year honours.
Both have three wins on the season but Johnson claimed a major at the US Open. He also is in the box seat to make it four wins and add the FedEx Cup after he surged to the outright lead at East Lake.
Johnson shot a three-under-67 to push to seven under for the tournament, now one clear at the top.
Fellow American Kevin Chappell (68) sits second at six under with Kevin Kisner (70) and Hideki Matsuyama (71) tied third at three under.
Day was travelling okay on Friday with one birdie and one bogey through seven holes before things unravelled.
After his tee shot found the water he attempted to hit driver off the deck from the rough and found tree trouble.
After another shot left him off the green he picked up the ball and started walking into the clubhouse, leaving the premises in haste.
"There was a couple of drives out there where - just off the top of the transition, felt a bit of a sharp pain in my back," Day said after round one.
"When I get to the top of the swing, as soon as my hips start to unfold and then there's that bit of separation, it just crunches down. It just hurts."
Adam Scott is now the lone Australian in the field, already seven shots back at even par.
A 71 on Friday means Scott must get hot over the weekend to have any chance at the rich payday.
