Paul Casey's spectacular return to form continued as the Englishman backed up Thursday's round of six under with a second consecutive 66 to take a three-shot lead into the weekend of Memorial, Muirfield Village.
It was a forgettable day for Rory McIlroy, though, as the world number six crashed to a six-over par 78 thanks to three consecutive double bogeys on his front nine wrecked all of the previous day's good work.
His round was incredibly 15 shots worse than his opening 63 as bogeys at 10 and 18 - his first and ninth - came either side of a hat-trick of double bogeys stretching from the par-four 13th to the par-five 15th.
Worryingly for the two-time major winner, it was in-keeping with his trend on the PGA Tour this year of having shot 40 or above on either nine of Friday's round in five of his last six starts in America. Perhaps not so worryingly, he has finished in the top 10 on every occasion that has happened.
While McIlroy clearly struggled as he went out early in Ohio, Masters champion Bubba Watson continued to impress in a stellar season for the Florida native as his 69 was enough to take solo second after two days, meaning he and Casey will comprise Saturday's final pairing.
It could've been even better for Watson had he not ended a typically erratic back nine with back-to-back bogeys to allow Casey breathing space - although McIlroy displayed in some style how a three-stroke advantage can be obliterated in no time at all on the professional Tour.
Denmark's Thorbjorn Olesen was impressive on day two also, as his 67 backed up Thursday's round of one under to leave him among a cluster of American's - including Hunter Mahan - in tied sixth.
Japan's Hideki Matsuyama - who led last week going into the final round at Colonial - also managed a 67, leaving him alongside Martin Flores of the US - five strokes adrift of Casey.
World number one Adam Scott can by no means be ruled out of contention either at five under, after his 70 that included five birdies and three bogeys.
Currently, though, it is England's Casey out in front alone as eight birdies, an eagle and two bogeys saw last year's Irish Open winner in with another 66. Despite his 12 wins on the European Tour as well as being part of Europe's Ryder Cup winning team in 2006, the Cheltenham-born 36 year old has only managed one win on American soil.
That was in 2009 - at the Shell Houston Open - so he will feel a victory is long overdue in the States. It will cap a superb return to elite golf for Casey, who missed months of 2012 after dislocating his shoulder in an unfortunate skiing accident.
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