Heckenberg, 28, played in all three of Scotland's matches in the 2000 World Cup. Hull KR centre Rhys Lovegrove has also been forced out with injury. However, Quins new boy Mick Nanyn remains in contention for the trip Down Under.

The Scots have also withdrawn Wigan winger Mark Calderwood after his call-up into England's train-on squad. He is not guaranteed to make the final cut but Scotland manager Richard Thewlis said: "We only want players who are committed to Scotland, so he's out of our squad."

Coach Steve McCormack's initial 40-strong squad was already hit by the loss of Workington back-rower Iain Marsh, with a broken arm, while Richard Fletcher (Widnes), Spencer Miller (Whitehaven) and Graeme Horne (Hull) all pulled out for personal reasons.

McCormack is set to name his final 24-man squad on October 8.