Collingwood's Callum Brown will undergo shoulder reconstruction surgery this week and miss the rest of the AFL season.
Brown suffered a dislocated left shoulder during the dying stages of Sunday's 29-point defeat to traditional rivals Carlton at the MCG.
The 23-year-old saw a specialist on Monday to assess the injury.
It is similar to the one that caused Brown's younger brother and teammate Tyler to undergo season-ending surgery in June.
“It popped out and popped back in again,” Magpies high performance manager Kevin White said.
“Scans revealed today some significant damage, which will unfortunately see Cal undergo shoulder surgery … later on this week.
“It's unfortunate news for Cal that will put an end to his 2021 season.
“Like his brother Tyler, he'll follow suit with that shoulder reconstruction surgery and look to come back bigger and better again in 2022.”
Josh Thomas was also hurt in the loss to Carlton, suffering concussion from a collision with teammate Darcy Cameron.
Thomas will be sidelined for a minimum 12 days under AFL concussion protocols but the Magpies are confident it is a mild concussion.
Thomas will miss Friday's game against Port Adelaide at Adelaide Oval, while Brody Mihocek (abdomen) and Will Hoskin-Elliott (back) will be tested later in the week.
Jeremy Howe (hamstring) and Will Kelly (quad) are at least another week away from overcoming their injuries.