Australia flanker David Pocock will miss the upcoming Test series against the British and Irish Lions after rupturing an anterior cruciate ligament while playing for the Brumbies on Saturday.
Pocock was carried off with a knee injury in just the 13th minute of his side's 35-6 Super Rugby win over the Waratahs after a collision with international team-mate Adam Ashley-Cooper.
His club confirmed on Sunday that the Wallabies openside would be out for the rest of the season, which would include missing the eagerly-anticipated clashes with Warren Gatland's tourists, as he needs to undergo surgery.
"To hurt my knee so early in the season is obviously disappointing, particularly considering how well the team has been playing," Pocock said.
"The medical staff have given me plenty of time to make a full recovery so my focus has to turn to making that a reality. We had 17 different surgeries during the off-season so I've got faith in the club to get me back to full strength."
The news will come as a major blow to Australia coach Robbie Deans.
Pocock has marked himself out as one of the top number sevens in the international game, with his performances putting him on a par with New Zealand's World Cup-winning captain Richie McCaw.
Waratahs back-rower Michael Hooper and Liam Gill of the Reds would be the leading contenders to replace Pocock, while veteran George Smith, who played in the 2001 Lions series, could also be in the frame after returning to the Brumbies on a short-term deal from Japan.