Pratley Set For 2 Months Out With Injury
He first suffered the shoulder injury in January 2009, and was expected to be out for 10 weeks, but he returned in half of that time.
Pratley has now been advised to take action to prevent further damage.
The news comes as a big blow to new boss Paulo Sousa as Pratley was always a first team starter when fully fit.
Pratley's injury gives an opportunity to the likes of Joe Allen and new signing Jordi Lopez to impress early on in the new Championship campaign.