Wilkin has been with St Helens since 2002
Jon Wilkin has added to St Helens' injury worries after damaging a calf during an England training session.
The back row forward was hurt in the last five minutes of the two-day camp and is now being assessed by Saints.
St Helens team-mate Leon Pryce pulled out of the camp after aggravating a groin injury in Saturday's Super League win over Catalan Dragons in Perpignan.
Pryce, who was making his first appearance since last July, could be out of action for another two months.
In addition, Sia Soliola is facing a month on the sidelines with an ankle injury, and former Harlequins prop Louie McCarthy-Scarsbrook is doubtful for Friday's game against his old club because of a shoulder injury.
There is some good news for Saints, however, with Australian prop Josh Perry - a close-season signing from Manly Sea Eagles - set to make his debut on Friday, although he is likely to only be used sparingly at first after recovering from a leg injury.