Billy Slater has been running at 15km/h on a treadmill but the star fullback admits time could beat him in his race to be fit for the World Cup final at Old Trafford next Saturday.

Slater, whose wayward pass in the 2008 tournament decider helped New Zealand to a 34-20 victory, will be given every opportunity to play by Australian coach Tim Sheens but said he won't put himself ahead of the team.

The 30-year-old has borrowed an ice machine from teammate Nate Myles and has been icing his injured left knee up to eight times per day as well as having regular physiotherapy.

Kangaroos physiotherapist Tony Ayoub said Slater had been running on a treadmill but the Melbourne Storm star conceded he needed to keep rapidly improving to play against the Kiwis.

"I am going to give myself the best opportunity to get there but I am not going to play if I can't play properly," Slater said.

"I am quite happy with how it has improved but, at the same time, I haven't tested it properly yet.

"The test is when you accelerate and you are at some speed and you are changing direction and all of that stuff."

Ayoub said he gave Slater a "realistic chance" of playing. "He is going really well," the physiotherapist said. "He had a run yesterday for about 20 minutes on the treadmill. He was pushing himself. I planned to do 12 minutes and he ended up doing 20, and he was going faster than I anticipated. He was doing 15km/h.

"Probably day one or day two last week, he wasn't good. His knee had blown up in a short period of time, which isn't a good sign but the MRI came back all clear and he has got full range, he doesn't have any pain. You have got to give the kid credit, he works hard.

"He ices five, six, seven or up to eight times a day. He is certainly professional about it. If he thinks he can play he will make that decision himself and knowing the gravity of the game we are about to play, you don't want to go out there with anyone who isn't fit."

If Slater is fit, Greg Inglis will move from fullback to left centre, squeezing Brent Tate out of the side or forcing him to the bench.

Australian secondrower Greg Bird only played 36 minutes before being replaced. Kangaroos coach Tim Sheens said he only had a cork.

Kangaroos captain Cameron Smith said the team wouldn't use their 2008 World Cup defeat by New Zealand as motivation when the two nations meet again in the final.

"2008 was a long time ago and I know we won't be using that as motivation," Smith said.

"I am sure it will be in a few of the guys' back of their minds but we have got a totally different team and different coach so our motivation will be the best Australian team we can be."