The American, a five-time major champion, finished the opening day with the clubhouse lead on eight-under-par.

Despite his superb performance, 2013 The Open winner Mickelson was left visibly frustrated when a 15-foot birdie putt on the final hole came back out off the lip to deny him a record round.

American Patrick Reed and Germany's Martin Kaymer are joint second on five-under as players took advantage of favourable conditions on the course.

America's defending champion Zach Johnson looked set to join the duo on the score but bogeyed the last to drop to four-under.

World number four Rory McIlroy threatened to challenge the lead for spells during his round but eventually entered the clubhouse six shots off the pace on two-under par in his first competitive appearance since he dealt a huge blow to golf's future on the Olympic programme by claiming the Rio 2016 tournament "didn't matter".

Adam Scott of Australia, another player to demonstrate apathy towards golf's first Olympic appearance for 112 years, is also on two-under, while two-time major champion Jordan Spieth carded a 71 to finish on even par.

Bubba Watson of the US raced out of the blocks and made full use of a favourable front nine as he was five-under through six holes but could not capitalise on the early momentum, ending the day with a one-under 70.

It proved to be a difficult outing for Australian Jason Day, the current world number one, who struggled on the trickier back nine and finished tied 96th on two-over.

"I felt like it was kind of easy," Mickelson said. 

"I didn't try to do too much.

"It was a beautiful day, and I took advantage of it.

Describing the agonising miss on the 18th, the 46-year-old added: "It was right in the centre of the hole with a foot to go.

"I've seen all these highlights and I feel like crying.

"That was a chance to do something historical right there, and to miss it that way."