Before London Welsh confirmed the extent of his injury, head coach Lyn Jones was trying to remain upbeat on his star player.
"We're hoping for the best, but if it's the worst he's not the first player to get injured and we'll just have to be patient and deal with it," Jones said, in quotes carried on the club website.
"These are things you've got to deal with in rugby. You've got to deal with thunderbolts all the time.
"No player wants to get injured in a pre-season friendly because it's hugely frustrating because of all the hard work that's been done leading up to the start of the season.