The former Liverpool winger, who has not played since December, expects to return for Turkish club Galatasaray this weekend but has only a handful of games in which to prove his fitness before the South Africa finals start on June 11.
"This injury has come at a bad time for me so I've got to work hard to try to secure myself," Kewell, who underwent surgery on the groin earlier this year, told Australian television on Tuesday.
"Basically I've got one of the biggest tournaments coming up now. It's a chance for me to show this club what I'm capable of doing.
"I feel like I can do that. I just needed a little rest to get my body back into shape and now it's back into shape and it's nearly there, so I'm really looking forward to this World Cup."
"Obviously as a youngster I did well enough to achieve certain things, but I still feel like I've got more in me to produce better football now than what I did when I was younger," he said.
"So hopefully the good achievements haven't even started with me yet."
