Martin Kaymer soon had extra reasons to be looking anxiously over his shoulder in the final round of the US Open at Pinehurst.
Rickie Fowler and Erik Compton were the only players to break par in Saturday's third round, matching scores of 67 lifting them into second place on three under par, five shots behind Kaymer.
But with the course playing easier on Sunday thanks to watering of the greens overnight and in the morning, three of the first nine players to complete their final rounds shot below 70.
England's Matt Fitzpatrick, the only amateur to make the cut before competing as a professional in next week's Irish Open, carded a 69, while playing partner and former Open champion Louis Oosthuizen bogeyed the last for a 67.
American Daniel Berger went one better with a 66, the 21-year-old covering the back nine in 32 despite a bogey on the 14th to finish seven over par, all the damage done by a third round of 78.
Out on the course, former Masters champion Zach Johnson had recorded the first hole-in-one of the week on the ninth, his tee shot pitching well left of the flag but catching a slope and rolling 20 feet into the hole.
England's Ian Poulter had birdied the first and fifth to move to two over par, while American JB Holmes had picked up shots on the same holes to move into the top 10 on one over.
The last man to lose a five-shot lead after 54 holes of a US Open was Mike Brady in 1919, but just two of the last nine leaders after three rounds had gone on to win the title - Tiger Woods in 2008 and Rory McIlroy in 2011.
Kaymer and Fowler made up the final pairing at 3:25pm local time, with the 34-year-old Compton - who has undergone two heart transplants - alongside Sweden's Henrik Stenson, who was six off the pace on two under.
Stenson would overtake Adam Scott as world number one by claiming his first major title, as long as Scott finished outside the top four.
Defending champion Justin Rose had conceded he was playing for second place after starting the day nine shots off the lead, but an eagle from 25 feet on the fifth lifted him to one under par for the tournament.
That was seven behind Kaymer after he opened with two pars, while Stenson had joined the group in second on three under with a birdie on the third, where the tee had been brought forward to tempt players into trying to drive the green.