A mystery illness is threatening the career of Kiwi fullback Richie Barnett.
Unshakable fatigue has dogged Barnett for the past six months, transforming his English Super League season into a nightmare.
He has seen a London specialist who treats numerous British Olympic athletes and is hoping the doctor will get to the root of his problems.
"It has been a nightmare," Barnett said from England where he plays for the London Broncos. "Sometimes I haven't played even a whole game. I play parts and come off.
"I have thought about everything. It is amazing the things you think about when these sort of things happen. I have even thought what happens if it is life threatening.
"I am trying to remain positive about it and hopefully it is something they can rectify."
The illness has hurt the fullback's form. Barnett, 31, said he had been playing "pretty average".
"I can make a run and then I will have had it afterwards," he said. "I will struggle to get to the next play. If the ball goes one way, I struggle to get to that side."
The fatigue problem has come at a bad time for Barnett.
The former Aucklander is off contract at the end of this season and will be looking to nail a new two-year deal when the anti-tampering period ends in England on August 1.
"There has been a fair bit of interest and in the next month or two I will find out whether I am going to stay here or go to another club," he said.
The Broncos are keen to re-sign him. There has also been interest from the sport's traditional northern power base in England. Leeds is likely to bid and the Bradford Bulls were interested in Barnett last season. However, the Bulls look to have filled their overseas quota.
The Broncos future is likely to be a major consideration for Barnett.
The club has struggled in London and its Virgin sponsorship deal finishes at the end of next season.
Barnett was in excellent form last year but hamstring problems disrupted his season and prevented him leading the Kiwis in the one-off tests against France and Australia.
One of the best outside backs produced by New Zealand in recent years, Barnett wants to play the Kiwis' end-of-year test programme.
And the Kiwis badly need him. He is the obvious fullback selection for national coach Gary Freeman who was desperately keen to have the former Sydney Rooster and Cronulla Shark in his team last year.
If he is fit and the Broncos are out of the Super League's top six playoffs, Barnett said he would be available for the first international against Papua New Guinea in Rotorua on October 5. The Australian test is a week later in Wellington. The Kiwis then head to Great Britain and France.
A lot will hinge on if he can overcome the fatigue.
"It has probably been the worst thing I have ever had. I know I can play better and feel as though I can do more but I can't actually do it," he said.
"I don't feel like playing and the enjoyment has certainly gone out of it. I am struggling and it is just not me. I am usually really enthusiastic about things and looking forward to training and playing.
"I am just fatigued all the time. It has been six months but it seems like 12 months. It has been dragging on."
Barnett did not train last week and isn't playing the Broncos' round 16 game as he attempts to get to the bottom of the problem.
After 15 rounds of the Super League, the Broncos lie seventh on the table with 15 points. They are 11 points adrift of competition leader Bradford but only three points behind sixth-placed Widnes.
The top six English sides make the playoffs and Barnett believes his club can be involved at the end of the season.
"I think we will be right up there if we don't lose any of our players," he said.
"We are travelling not too badly. I am sure we have a lot more left and there is not much (in terms of points) between us and Widnes."