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, replaced by fellow Australian Peter Betham.
"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."
The Tigers held off the reigning Champions Cup winners, despite a starring role from Dan Carter, who scored an incredible solo try for the French.
Former Wallabies lock Sitaleki Timani notched a try to help Clermont win a high-scoring epic against Bordeaux, 49-33.
Hooker Nathan Charles played three minutes off the bench for Clermont in the win, while Wallabies and Bordeaux winger Adam Ashley-Cooper and former Test lock Luke Jones missed the clash.
James O’Connor lined up on the wing for Toulon in his first match in three weeks, as Toulon capitalised on an early one-man advantage in a 15-5 slog against Sale.
Lachie Turner played at fullback for Exeter, as the Chiefs went down 19-18 after a last-gasp Ulster drop goal, while Dave Dennis came off the bench.
Jesse Mogg made his return from injury for Montpellier in a 22-16 win over Leinster, playing 14 minutes off the bench, while Nic White played at halfback.
European rugby pays its respects to Anthony Foley pic.twitter.com/qA2Ayufdvv— Champions Cup (@ChampionsCup) October 23, 2016
It was an emotional weekend for Munster, who officially farewelled coach Anthony Foley, who passed away from a heart problem in the team hotel in Paris last week.
The Irish province went on to beat Glasgow 38-17 on Sunday morning (AEDT).
Leroy Houston came off the bench for Bath, as Welsh International Rhys Priestland kicked the English side to a 22-6 victory over Bristol.
Former Wallabies skipper Ben Mowen played number eight for Pau in a 27-12 loss to Cardiff in Wales.
Prop Salesi Ma’afu came off the bench for Gloucester in a bonus point 37-8 win over Benetton Treviso, playing 17 minutes on debut for the English club.
James Horwill skippered Harlequins in a comeback that fell just one point short in Scotland, with the London team scoring 21 second-half points after trailing 31-14 at the break, only to go down 35-34.
Horwill made 13 tackles and won a turnover in the loss, which left them with a 1-1 start to the tournament.
Mike Harris’s Lyon were undone by a Keelan Giles hat-trick in their match against Ospreys.
While Harris did not play in the match, former Queensland backrower Curtis Browning scored one of the French side’s two tries.
Former NRL star Ben Te’o crossed over for Worcester, in an agonising one-point loss to Brive.
Former Wallabies teammates George Smith and Mark Gerrard faced off in Japan, with Gerrard at fullback for Toyota Industries Shuttles and Smith at number eight for Suntory.
It was Smith who had the last laugh, with the Sungoliath takinga 52-15 win over the Shuttles, though Gerrard scored a try for his side.
Digby Ioane played 26 minutes for Honda in a 24-37 loss to Kobe Steel, a defeat that keeps them anchored to the bottom of the Top League ladder.
Scott Higginbotham made 12 tackles at number eight for the NRC Green Rockets in a 15-15 draw with Kubota.
Anthony Fainga’a started at 13 for Kintetsu in a 15-12 win over Munakatam, while two-Test lock Daniel Heenan played a half in Panasonic’s 29-16 win over the Canon Eagles.
Wycliff Palu played eight for the Toyota Verblitz as they flogged the Coca-Cola Red Sparks 57-15.
Former Queensland player Ben Lucas was yellow-carded, playing fullback for the Verblitz.