BROOKLINE, MASSACHUSETTS (REUTERS) - Phil Mickelson has faced a huge backlash for his decision to join the Saudi-funded LIV Golf Invitational Series but was greeted with open arms by wide-eyed spectators during a practice round on Tuesday (June 14) ahead of US Open.

In glorious sunshine and with barely a breath of wind at The Country Club outside Boston, the six-times major winner had all eyes on him when he set off on a practice round under the guard of four police officers.

When Mickelson was introduced at the first tee, a hearty round of applause along with shouts of "we love you" and "let's go Phil" were returned with a series of thumbs-up from the long-time fan favourite who was all smiles.

Mickelson's public image took a hit in February when the author of an unauthorised biography on him released excerpts from the book in which the American golfer called the Saudis "scary" but said he was willing to look past their human rights records to gain leverage with the PGA Tour.

Mickelson then took a self-imposed hiatus from the sport - even skipping his title defence at the PGA Championship - and only returned last week outside London for the inaugural event on the LIV circuit.

But the 51-year-old Mickelson's reputation appeared intact as he played his practice round in the company of fellow American Kevin Na, who also joined the LIV Golf series, and Spanish world number two Jon Rahm.

"He's got to make a living," Stephen Mahoney, a 67-year-old retiree from Massachusetts said of the Hall of Fame golfer's decision to join the lucrative breakaway circuit late in his career. "Whatever you can grab now, grab it."

Mickelson never flies under the radar at the US Open, the one title he needs to complete the career Grand Slam of golf's four majors, but the spotlight on him this week looks set to reach new heights.

"Let's go Lefty!" and "How about that Grand Slam this weekend?" shouted others as he made his way around the course.

But while Mickelson was enjoying plenty of encouragement at The Country Club, not everyone in attendance was as supportive.

"Very disappointed, I feel like he is ruining his legacy,"Alexandra Rautiola, a 36-year-old nurse practitioner from Massachusetts said at the second hole.

"It's sad to see because, second to Tiger (Woods), he has done the most for golf."