The Saints have 11 players aged 29 or over – twice the AFL average – and will need to make decisions on Grand Final heroes from 2009 and 2010 come the end of the season.
Clint Jones, Justin Koschitzke, Jason Blake and Stephen Milne are all coming out of contract and face uncertain futures beyond this season.
Lenny Hayes, who has the Saints' backing to play on, has said he will make a decision on his future at the end of this season.
"I think that's on everyone's radar and everyone would be well aware of that," Riewoldt told Fox Footy's On the Couch.
"Some of them are going to be forced decisions and some of them are going to be voluntary decisions.
"People come and people go and it's a bit of a revolving door, but they're decisions the club administration and coaches will make at the end of the year in consultation with the players."
Riewoldt said a decision on the playing future of Milne - who has been charged with four counts of rape stemming from a 2004 incident - would be made at the end of the season, based solely on his football.
Meanwhile, he backed Hayes to play on in 2014.
"It's a really tough one. I certainly hope so, purely from a selfish point of view," he said.
"I think he's still got a lot to offer in terms of his role within the team as just a player.
"But the character of the person, just to have him around the club is invaluable. I hope he goes again."
Riewoldt, who has played career-best football at times this season and is contracted until the end of 2014, said he was "taking a great level of satisfaction" out of his role as captain this season.
While St Kilda has battled to a 3-13 record, he said the season hadn't felt like a three-win campaign.
"As a senior player, you need to be able to find different motivations," he said.
"I'm taking a great level of satisfaction personally in being able to play a role with the young guys.
"Certainly there's a pride aspect in your own performance, and there's a responsibility as well.
"I was a young player once and I had great leadership from guys like Aaron Hamill and Robert Harvey and Fraser Gehrig and Stewy Loewe.
"The wheel turns and now it's my opportunity to play that sort of role. That's what motivates me."
Nathan Schmook is a reporter for AFL Media. Follow him on Twitter @AFL_Nathan