Peel, who started all three Tests for the Lions against the All Blacks three years ago, left the field after 45 minutes of Sale's stunning victory in France.
Having missed his country's summer tour to South Africa following shoulder surgery in April, the 27-year-old is now a major doubt for Sale's clash with reigning European champions Munster at Edgeley Park on Sunday.
Now there are fears that Peel could also miss Wales' autumn Tests against South Africa, New Zealand, Canada and Australia.
"Dwayne made a routine tackle after five minutes and took a heavy bang on the shoulder," said Sale coach Kingsley Jones.
"He was in real pain and couldn't continue. We will have to wait and see what the medical experts say."
Peel's injury could open the Wales door for fellow Lion Gareth Cooper as No 9 rival Mike Phillips has already been ruled out of the November internationals after knee reconstruction.