The winner of seven major championships and five more as a senior, Palmer has not won an event since 1988 and has not contended seriously in years.

The 77-year-old legend, who was making just his third competitive appearance this year, played only four holes on Friday at the Administaff Small Business Classic before retiring with a sore lower back.

"I think (this is it)," said Palmer, who finished out the round for the fans.

"I'll play some father-son events, some charity events.

And that's about it.

Right now, there's just no thoughts of any more tournament golf."

Known as "The King", Palmer won the 1954 US Amateur before joining the PGA Tour the following year.

He captured the first of his four Masters titles in 1958 and soon developed a legion of fans known as "Arnie's Army."

His most successful year was 1960, when he won his second Masters crown and only US Open title, when he rallied a final-round 65 to defeat the legendary Ben Hogan and a young Jack Nicklaus, who was still playing as an amateur.

He fell short of winning the "Grand Slam" that year, finishing second at the British Open and tying for seventh at the PGA Championship, the lone major he failed to win.

Palmer was victorious at the British Open in 1961 and 1962, while adding Masters crowns in 1962 and 1964, en route to 62 tour titles, the fourth-highest total in history.

The Latrobe, Pennsylvania-native cashed in on his growing popularity by teaming with sports agent Mark McCormack to become one of the best known athletes for commercial endorsements.

Palmer became the first golfer to win

1 million (£540, 000) in career earnings.

The PGA Tour annually gives an award bearing his name for the top money winner each year.

"I've been doing this a long, long time," Palmer said.

"First of all, to stand out there and not be able to make something happen is very traumatic in my mind.

"And when the people all want to see a good shot and you know it.

And you can't give them that good shot.

That's when it's time."

When he turned 50, Palmer joined the new Champions Tour and posted 10 victories, including the US Senior Open in 1980 and the Senior PGA Championship in 1984 and 1985.

His final title came at the 1988 Crestar Classic.

"I may stop playing now, start exercising and get in shape and see if I can at least enjoy the simple golf that I always like to play," Palmer said. "It's emotional for me because, you know, it's my life."

Palmer's last PGA Tour event was his 50th Masters in 2004.

He will continue to host the Bay Hill Invitational in Orlando, Florida.