A rain-softened course was protected by some fearsome pin positions as the third round of the US Open got under way at Erin Hills today.
Almost an inch of rain fell on the course overnight, but scoring conditions were far from easy as the likes of former champion Jordan Spieth and Lee Westwood tried to move into contention.
Fifteen of the 18 holes had been cut within seven yards of the edge of the green and despite the 68-man field being separated by eight shots, only former Open champion Louis Oosthuizen had been able to move into the top 15 after almost four hours' play.
Oosthuizen, whose sole major title to date came at St Andrews in 2010, birdied the first, fourth, seventh and eighth to move to four under par, while 2015 winner Spieth had covered his first 11 holes in level par.
Westwood had bogeyed the third and fifth before a superb tee shot on the 239-yard sixth - which played as the most difficult hole on Thursday - set up a birdie from 18 feet.
England's Paul Casey and Tommy Fleetwood shared the lead on seven under par alongside American duo Brooks Koepka and Brian Harman, the first four-way tie after 36 holes since 1974.
On that occasion Arnold Palmer, Gary Player, Hale Irwin and Ray Floyd shared the halfway lead, with Irwin going on to win the "Massacre at Winged Foot" on seven over par.
Oosthuizen, who lost a play-off for the Masters to Bubba Watson in 2012, carded his fifth birdie of the day on the 11th to get within two shots of the lead, with the final group still more than an hour away from teeing off.
The 34-year-old finished second in both the US Open and Open Championship in 2015, with his remarkable performance at Chambers Bay leaving him as the holder of two tournament records.
The only good thing about his opening round of 77 was that it was the lowest of his group, with Tiger Woods shooting 80 and Rickie Fowler an 81 for a combined total of 28 over par.
And despite starting his second round with bogeys on his first two holes, the South African bounced back to record a superb 66 which he matched in the third round.
That gave Oosthuizen a record total of 132 for the middle two rounds and after bogeys at the second, third and fourth in the final round looked to have ended his chances, he carded six birdies in the last seven holes for a record-equalling back nine of 29 and outright record of 199 for the last 54 holes.