Matt Toomua is facing a stint on the sidelines after suffering a knee injury in his second game for English rugby club Leicester.
The former Wallabies playmaker departed halfway through the first half as his Tigers scored a 27-17 European Champions Cup victory over Dan Carter's French side Racing 92 at Welford Road.
Inside-centre Toomua was injured after being tackled in the 18th minute and took no further part in the game.
"Matt stopped to try and step, and something has given way in his knee," Leicester coach Richard Cockerill said.
"We don't know the extent of that. We will find out in the next couple of days."
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The injury continues a tough introduction for European rugby for the 31-Test Wallaby after he was sin-binned for a late tackle during his debut against Glasgow nine days ago.
The win over French champions Racing puts Leicester's quarter-final hopes back on track after their 42-13 drubbing by Pool One rivals Glasgow.
The Tigers have got it all to do in a group that also includes Munster, and their December back-to-back meetings with the Irish province could prove pivotal.
