ST KILDA senior coach Alan Richardson has confirmed ruckman Billy Longer will miss the remainder of the 2015 season due to a shoulder injury.

The 22-year-old, who has played 18 games in a breakout year, will have surgery on his right shoulder on Monday morning.

Head physiotherapist Andrew Wallis said Longer’s shoulder had become progressively worse as the season wore on but does not expect it to linger into 2016.

“Billy is having a labral repair which is effectively a reconstruction,” Wallis told SAINTS.com.au.

“This has an associated reasonable rehabilitation period and therefore the decision has been made now so that he has every opportunity to complete a full pre-season.”

OPEN TRAINING: Saturday August 29

The decision to send Longer into surgery potentially allows Jason Holmes to play the last three games of the season alongside Tom Hickey, while Lewis Pierce is next in line should another injury occur.

Longer joins Jack Billings (shin), Tom Lee (ankle), Brenton Payne (ankle) and Nathan Wright (finger) as players who have been ruled out for the season.

In other selection news, Richardson strongly indicated on Thursday morning that David Armitage (shoulder) and Sean Dempster (nose) would return to face Sydney, while Dylan Roberton, Jack Sinclair and Jack Lonie are in the mix. 

UPDATED: Injury list

"We are starting to create some depth but we need to get much more," Richardson said.

"There is real clarity about what we are trying to achieve as a team and we need to be strong against strong teams in the remaining games."