Sydney veteran Heath Grundy has become the latest player to take time away from the game to deal with mental health issues.
Grundy will miss Saturday night's crunch clash with Collingwood at the MCG, and it remains unclear when he will return.
The 32-year-old will continue to train with the team, but his absence against the Magpies is a huge blow to the faltering Swans.
Lance Franklin, Tom Boyd, and Alex Fasolo are other players who have taken a break from the game in the past in order to deal with mental health issues.
Sydney coach John Longmire hopes Grundy will return before the end of the season.
"To put your hand up and ask for help can be a really challenging thing to do," Longmire said.
"We believe it's really important to provide an environment and the support to enable our players to do that."
The Swans welcome back Alex Johnson for his first senior game since the 2012 grand final, while Kieren Jack and Jarrad McVeigh also return.
Irishman Colin O'Riordan (hip) and Zak Jones (suspension) join Grundy out of the side.
The Magpies replaced Jeremy Howe (concussion) and Matthew Scharenberg (knee) with Jack Madgen and Brayden Sier.
North Melbourne have been boosted by the return of key forward Jarrad Waite (calf) for Saturday's clash with Brisbane at the Gabba.
Richmond have lost premiership duo Dion Prestia (ribs) and Nathan Broad (calf) for Friday night's blockbuster against the Cats.
Connor Menadue and Sam Lloyd come into the side.
Geelong lost Tom Stewart (foot) and Quinton Narkle (personal leave).
Crows defender Brodie Smith, who hasn't played at AFL level since rupturing his ACL late last year, will return for Saturday's showdown against Port Adelaide.
But Adelaide will be without Paul Seedsman (hamstring), Kyle Cheney (suspension), and Mitch McGovern (shoulder).
Injury-plagued midfielder Nathan Freeman will finally make his AFL debut when he lines up for the Saints against the Bulldogs on Saturday night, with Jimmy Webster also called up.
Roarke Smith, Tory Dickson, and Lin Jong all return for the Bulldogs.
GWS spearhead Jeremy Cameron will make his return from suspension against Carlton at Etihad Stadium on Sunday, but the Giants have lost Sam Reid (knee), Tim Taranto (knee), and Dylan Shiel (ankle) to injury.
West Coast have been boosted by the return of Lewis Jetta and Luke Shuey for Sunday's western derby against Fremantle, while goalsneak Liam Ryan is in the extended squad for the first time since crashing his car.
The Dockers could welcome back Matt Taberner from a broken foot.
Gold Coast have lost David Swallow and Rory Thompson to injury, while Steven May is out suspended for Sunday's match against Melbourne.
But Pearce Hanley will play his first senior game since dislocating his shoulder in round three.
Melbourne will be without Jake Melksham (hamstring).
