"We're in a difficult situation," John Best, the Australia team doctor said yesterday. "We don't want to make the wrong decision. We don't want to push it too hard."
Best said the injury was recovering well but he was still unsure whether Horan, who faces a fitness test tomorrow, would be able to complete a competitive match.
Australia are due to play one warm-up match in France before facing the Five Nations' champions in Paris on 14 November. They play England at Twickenham a week later.
Horan's loss would be a major blow to the Australians who are already missing the quality of Matthew Burke and Ben Tune.
Three brothers will play for the Welsh club Llanelli against Stade Francais, the French champions, in the European Cup on Saturday. The twins, Roddy and Neil Boobyer, will play in the backs with their brother, Ian, at open- side flanker in a game Llanelli must win to have any chance of making the quarter-finals. It is the first time the three have played together for the Scarlets.
Neil, capped six times for Wales at centre, fills in at stand-off in the absence of the injured Craig Warlow and Steve Jones.
Stade Francais are already in the last eight but need a win to ensure a home quarter-final.Reuse content