CHARLOTTE, North Carolina, Aug 12 (Reuters) - Jason Day began the day in the final threesome, two strokes off the lead, and had the usual ups and downs on Saturday before his quadruple-bogey at the Quail Hollow gauntlet known as the 'Green Mile'.
Day began the stretch at the par-four 16th with his third successive birdie to reach five-under but danger was just around the corner. The Australian bogeyed the par-three 17th and finished with a nightmare quadruple-bogey eight.
That adventure started with a wayward drive that took him into the trees, leading to two horrendous shots and a penalty stroke, a weak escape from choking rough, a weak chip and two putts.
Day lost five shots over the two holes and finished seven off the pace.
"He played good coming in and then gave it all away, so that's tough," said playing companion Kevin Kisner.
A shell-shocked Day, usually accomodating with the media, walked off hand-in-hand with wife Ellie without taking questions.
Tournament leader Kisner was not unscathed, either.
Sailing along with a two-shot lead, Kisner pulled a shot into the water at the 16th and had his bogey-putt spin out of the hole for a double. At 18, he bounced an approach off a stone bridge that saved him from another splash but sent him into deep rough and a bogey.
That slight reprieve allowed him to cling to a one-shot lead over Hideki Matsuyama and fellow American Chris Stroud going into Sunday's final round.
Entire threesomes fell victim to the 18th.
Jordan Spieth, who came to Quail Hollow looking to complete a career grand slam of majors, England's Tommy Fleetwood and veteran Vijay Singh all double-bogeyed the last.
Spaniard Jon Rahm and playing partner Steve Stricker doubled as well. As did Paul Casey, whose two-under for the tournament turned into even-par.
Australian Adam Scott joined the double-bogey brigade as one of 12 scores at the 18th of double-bogey or worse.
Not everyone was left cursing the 18th, with first-round leader Thorbjorn Olesen (three-over) and Patrick Cantley (two-over) both signing off with birdies.
(Editing by Peter Rutherford)