Lewsey left the ground with his right knee in a brace, amid fears that he had suffered a strained medial ligament.
Lewsey will have a scan on Sunday or Monday but it would appear that he could join a lengthy England casualty list for the New Zealand clash.
England head coach Andy Robinson has already lost the likes of Jonny Wilkinson, Olly Barkley, Steve Borthwick and Stuart Abbott from his plans to meet New Zealand.
But the possible loss of Lewsey would leave a considerable void in England's back three as they begin their countdown towards next year's World Cup defence.
"I will have to wait and see what the scan says, but I am being as positive as possible," said Lewsey.
"It was a twist. It was one of those things you can't predict and the pain wouldn't go away when I was trying to run at top end.
"My gut feeling is that is it not as bad as it looks, but we will just have to wait and see. I might be training by next Tuesday or Wednesday, I just don't know."
Lewsey's injury completed a miserable afternoon for Wasps in southern France, as they suffered a sixth Heineken Cup defeat from their last seven European away games.
Jeremy Staunton kicked three penalties and substitute Alex King landed a late kick that secured a losing bonus point, but there was little to please Wasps as they slipped to third place in Pool One.
Perpignan scored a second-minute try from lock Colin Gaston, and that ultimately made the difference in a poor match ruined by Wasp's poor handling.
"The start was a nightmare for us - conceding a try within two minutes was exactly what we didn't want," said Wasps coach Shaun Edwards.
"Our turnover rate was poor, and if we had executed some pressure then Perpignan would have cracked, but we didn't. There are no excuses."