Jason Day of Australia plays his shot from the fourth tee during the Second Round of the BMW Championship at Conway Farms Golf Club on September 18, 2015 in Lake Forest, IllinoisJason Day of Australia plays his shot from the fourth tee during the Second Round of the BMW Championship at Conway Farms Golf Club on September 18, 2015 in Lake Forest, Illinois (AFP Photo/Patrick Smith)
Chicago (AFP) - Jason Day rolled in a 43-foot eagle putt at the 18th hole to equal the lowest 36-hole total in PGA Tour history and seize a five-shot lead in the BMW Championship.
The red-hot Aussie, who finished off a first-round 61 on Friday morning, signed for an eight-under par 63 for the second round at Conway Farms for an 18-under total of 124.
That put him five in front of US tour rookie Daniel Berger, who carded a 64, and Brendon Todd, who posted a 63 for 129.
"I don't know how else to explain the way I've been playing," Days said. "I feel very free, like there's no stress. There's obviously stress, but I'm enjoying it."
Day also had a leg up on world number two Jordan Spieth and number one Rory McIlroy, who could see the currently third-ranked Australian leap-frog to the top of the world rankings with a victory on Sunday.
Spieth, who played alongside Day in the first two rounds, fired a second-round 66 for a share of fourth on 132, alongside fellow American Kevin Na, who also carded a 66.
McIlroy fired a 65 to head a group sharing ninth on 133.
Day, whose four victories this season include his first major title at the PGA Championship last month, had seven birdies and one bogey to go with his eagle in the second round.
His 124 matched the record 36-hole total set by Pat Perez in 2009 and equaled by David Toms in 2011.
But Day said he wouldn't be thinking about that as he headed into the weekend.
"It's over now," he said. "I've got to look ahead to tomorrow's round now."
Spieth, who also eagled the final hole to stay within striking distance, said Day had been so impressive in the two rounds they played together that it would have been worth the price of a ticket to watch.
"I feel like I should be paying to watch this event," he said.
Their day started when they returned to their final first-round hole, the par-four ninth, where Day needed to hole his second shot to shoot 59.
His 45-yard pitch shot from rain-soaked rough didn't make it and he settled for a par that still gave him a career-best round of 61.
"It sounds like everyone is disappointed," Day said. "I'm like, jeez."
While Day, 27, is chasing the world number one ranking, he already tops the standings in the US PGA Tour's FedEx Cup -- the playoff race that will be capped by next week's Tour Championship where a $10 million bonus will be on offer to the series winner.
He opened the playoffs by winning the Barclays on August 30.