(CNN) -- Former Olympic medallist Brendan Foster has told CNN he will try to persuade Haile Gebrselassie to stay in athletics after the Ethiopian distance runner announced his shock retirement.
The marathon world record holder, who won Olympic gold in the 10,000 meters in Atlanta and Sydney, said he was quitting the sport after dropping out of Sunday's New York marathon with a knee injury.
But Foster, who called Gebrselassie "clearly the greatest athlete of all time" said he hoped the 37-year-old, who set 27 world best times in his career, would still compete in the London 2012 Olympics.
"We'll never see his like again, that's the truth," he told CNN. "He has graced this sport, he's a fantastic man as well as a great athlete. He's a diamond, really."
Gebrselassie quit the marathon after 16 miles and later told reporters: "I don't want to complain anymore after this, which means it's better to stop here."
But Foster, who has commentated on all of Gebrselassie's major races, is hoping it was a knee jerk reaction.
"I was very surprised and very disappointed," he added. "A couple of weeks ago he ran the Great North Run, which is a half marathon. He ran 59 minutes, he won easily and I thought he was running as well as I've seen him run for a long, long time.
"He was talking about coming back to London in 2012 and trying to win the marathon in the Olympic Games.
"I think he's had an injury going into the [New York] race, even though he was really running well before he went there, and I just hope this is an emotional reaction. I've already put a call in to his manager.
"I don't see any reason why the great Haile Gebrselassie, when he's still able to run 59 minutes for 13.1 miles, there's absolutely no reason why he should retire. He loves it, he runs every day."
Foster told CNN that if New York were to be Gebrselassie's last race, it would be a disappointing end to an unparalleled career.
"He's been a privilege to know and I think he should go out on a higher note than dropping out of a race. He's the sport's biggest asset," Foster said.
"We haven't had enough of him yet. Frank Sinatra came back many times. There's never been an athlete as good as him retiring. Let's hope Haile gets excited again -- he's allowed to change his mind."