NAIROBI, Feb. 1 (Xinhua) -- Double Olympic 800m champion David Rudisha may have raced over the cliff, never to return to dominate the track competition again.

Though, the 29-year-old is yet to announce his retirement, Rudisha has not competed for almost 18 months and there is no sign on the horizon he will be ready for this year's season, which starts in May with the IAAF Diamond League in Doha, Qatar.

"It is like a kind of a nagging injury, every time I try to push myself to a certain level, I start feeling some pain," Rudisha told the Olympic Media Channel Friday in Eldoret.

Last May, Rudisha's manager Michel Boeting lifted the lead on the world 800m record holder (1:40.91), saying he does not expect him to compete until August 2018.

It is six months since the time set and Rudisha has shown little signs of returning to action. Instead, he has been enduring several visits to the doctors in Kenya and the Netherlands, which are yet to yield any success.

Rudisha has an injury to his upper hamstring muscle, a similar problem that saw him miss out to defend his crown at the 2013 World Championships in Moscow, Russia.

Now his coach Brother Colm O'Connell is worried Rudisha's career could be on the rocks hindered by the same injury plaguing fellow double Olympic gold medalist Andy Murray.

"He has to look at his long term future in terms of his health. I think that is a consideration he must look at. We have the case of Andy Murray in tennis and eventually, somebody has to maybe call it a day because it just too much," said coach O'Connell.

His coach now hopes Rudisha, who is the only man to have run under one minute and 41 seconds, will see the truth of the circumstances and call-out on his time.

"There is no point coming back and be there. If he is a championships runner and has a reputation, which he has to look at. He proved it in Rio Games coming back from injury largely based on his tactics because there were challenges and there were pretenders," he said.

However, Rudisha believes he still has the energy to go the extra mile and he is even dreaming of winning third gold at the Tokyo Olympics in 2020.

His manager Boeting last year said if there is one thing that still motivates him it's the Olympics.

"If you want to see his eyes light up, mention Tokyo," Boeting said. His coach concurs saying that Rudisha always accomplishes his dreams.

"Once David puts his mind on something, once it clicks into his mind, he is fantastic and he is able to go for it. That's it. But I think he hasn't reached that stage yet in his preparations," added O'Connell.

Should Rudisha win the mind battle and return, he will face a horde of young upcoming 800m runners and may find it hard to push away.

They include last year's fastest man Daniel Saruni, Africa silver medalist Emmanuel Korir and Commonwealth Games champion Wycliffe Kinyamal.