Linfield expect Conor Pepper to be out of the action for "several weeks".
The Irish Premiership champions confirmed on Saturday that Pepper has dislocated his shoulder.
The injury happened during a training session ahead of the Blues' league opener with Crusaders.
Updating fans on the club's website, Linfield boss David Healy said: "I want to advise our supporters that Conor Pepper will be out of action for several weeks as he has unfortunately dislocated a shoulder in training.
"He will receive all the support our medical team can provide him with and we will endeavour to get him back to action as soon as possible."
Pepper made 24 appearances last season after joining Linfield in the summer of 2020.
His last game was last Saturday's friendly defeat to Dungannon Swifts when he played over an hour, with Pepper also featuring in the club's European run this summer.
