Just seven players in the Australian Four Nations' train-on squad took the field for training at Redfern Oval on Wednesday.

The players were put through an excruciating run last week, but they were given a lighter run in a ball work session overseen by assistant coach David Furner.

There is plenty of uncertainty surrounding the make-up of Tim Sheens' Kangaroos, with injuries in key positions, particularly in the halves and at centre.

Michael Jennings went down for Penrith in last Saturday's NRL semi final, while Johnathan Thurston is also racing the clock to be fit for the campaign against New Zealand, England and Papua New Guinea in late October.

"It was pretty tough, it wasn't as bad as last week I don't think probably because we had the ball to break it up a bit," said vice-captain Cameron Smith.

"But still a big blow out, the last bit was quite tough, just got through it so two down one to go."

Incumbent Cooper Cronk is hoping to get first crack at halfback, while experienced outside back Brent Tate is aiming to revive his Test career with opportunities in the centres.

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