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.