WHEN David Lyons was told on the eve of the Bledisloe Cup match in Auckland this year that he had been diagnosed with deep-vein thrombosis, he admitted to being confused.

This is not your run-of-the-mill football injury, and he had only a limited understanding of the seriousness of the condition and was unaware that his career was suddenly in jeopardy.

At the time, it was assumed that DVT - which affects a sufferer's ability to travel - would put Lyons out of the game for some time. In short, his World Cup chances appeared to be nil.

However, regular treatment and a daily regimen of three blood-thinning injections has enabled Lyons to defy all odds and make the World Cup squad. And now he is set to appear at No.8 against Canada in Bordeaux - his first match since July.

It is a testament to Lyons's dedication that he has been able to get back on the field. However, he admits to some unsettling moments.

"Shortly after discovering I had DVT, I had my first procedure in hospital, where they clean it all out," Lyons said.

"At the time they thought I should be fine. But a week later it was completely back again, and it was clotting all the way [down my leg]. Then I was concerned it was going to take a long time for it to go away."

This prompted a second hospital visit, and this time the treatment worked.

"A lot of people don't know much about deep-vein thrombosis," Lyons said. "When I first found out, I didn't really know how bad it was. I thought it was maybe a couple of weeks and it would be gone. But after learning that it can be something that can cause problems for quite a while, it convinced me that I had to manage it pretty well.

"And I think I've done that, and am confident that I can handle it properly from now on."

How he got DVT remains a mystery, but Lyons knows that he must stick to a strict routine of taking medication three times a day.

"However, before any contact work at training, or before a game, I'll go off [the medication] for 24 days so that my blood levels go back to normal."

Lyons knows that this game is his last chance to convince the selectors that he will be of some worth to the team during the finals of the World Cup.

"I am just excited to be playing again. I'm pretty confident that if I get more chances in the tournament I can do well," Lyons said.

"The team has been going well, so all I can do is play to the best of my ability against Canada, so that the selectors keep me in their minds. I really want to show them I am worthy of more game time."