Tacoma (Washington) - Fifteen players had reason to thank Nick Hardy after the American amateur bogeyed his final hole to alter the cut line at the US Open on Friday.

Big-name players, including Sergio Garcia, Colin Montgomerie and former champions Webb Simpson and Angel Cabrera, were already planning an early departure from Chambers Bay after finishing 36 holes at five-over 145, which looked all but certain to be one shot too many for weekend action.

But 19-year-old Hardy, in the final group of the day, did them all a favour with his bogey, which was also enough to let him sneak above the cut-line on five-over.

The late change did not help Martin Kaymer, who is no longer the defending champion. Twelve months after blowing away the field at Pinehurst No. 2 in North Carolina, the German found Chambers Bay less accommodating as he carded rounds of 72 and 74.

He was not the only big name to struggle on the quirky course next to Puget Sound, with two-time Masters champion Bubba Watson also bowing out early for the third time in four years. Several other former champions also packed their bags early, including Graeme McDowell and Retief Goosen.

Meanwhile, Jason Day needed medical treatment after dramatically collapsing at the side of the fairway on the final hole of his second round, but hopes to play at the weekend.

Placed high up the leader board at three under for the tournament at the time, the 27-year-old Australian hit his tee shot at the par-three ninth into a bunker and then fell to the ground as he made his way down to the green below.

A medical team took several minutes to revive him before he staggered on, playing his bunker shot and two-putting for a bogey four.

He was given more treatment at the side of the green and taken away on a golf cart to sign his card for the round.

Day's agent Bud Martin later said: "Jason was diagnosed to have suffered from Benign Positional Vertigo. He was treated locally and is resting comfortably. His condition is being monitored closely and he is hopeful he will be able to compete this weekend."

Day, twice a US Open runner-up in 2011 and 2013, has been suffering from vertigo and dizzy spells for the last few months and has pulled out of tournaments before in the last year because of the condition.

AFP