GREATER Western Sydney has suffered another cruel injury blow on the eve of the 2021 season, with defender Adam Kennedy set to be sidelined for up to five months with a shoulder injury.

In a blow reminiscent of the one that forced ruckman Braydon Preuss to go under the knife last week, Kennedy has also undergone a shoulder reconstruction after sustaining the injury during last Thursday's session.

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Both will now likely miss the first half of the upcoming campaign, with the latest setback continuing a horror recent injury run for Kennedy after he was restricted to just six games last season due to a hamstring problem.

Small forward Brent Daniels is also set to miss the early stages of the 2021 season, including the side's crucial round one bout with St Kilda, after injuring his hamstring in the same brutal session last Thursday.

Daniels will be sidelined for six weeks and will join Kennedy and Preuss, as well as small forward Bobby Hill (concussion), first-year wingman Ryan Angwin (concussion) and experienced defender Phil Davis (knee) in missing this Saturday's behind-closed-doors practice match against Sydney.

Gun midfielder Lachie Whitfield will also be sidelined as he continues his recovery from a bruised liver, but captain Stephen Coniglio will play after returning from the AFL's new 12-day concussion protocol.