The Wallabies' openside was carried off in just the 13th minute of his side's 35-6 Super 15 win over the Waratahs after a collision with international team-mate Adam Ashley-Cooper.
Pocock is due to have a scan on the injury, and posted on Twitter: "Wow. Thanks so much for all the tweets. Was great to watch the team win like that. Off to get a scan now. Staying positive."
Initial reports suggest the 24-year-old has damanged his anterior cruciate ligament, which could be enough to sideline him for the rest of the Super 15 season and the eagerly anticipated clash with Warren Gatland's tourists.
Should Pocock be ruled out of the Test series it will be a major blow for 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 series against the Lions, could also be in the frame after returning to the Brumbies on a short-term deal from Japan.
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