Riewoldt and defender Dylan Grimes are the omissions from last year's leadership structure.
Brett Deledio is again vice-captain with ruckman Ivan Maric and 2013 best and fairest winner Dan Jackson also voted into the group.
Former Port Adelaide defender Troy Chaplin is the new addition in his second season as a Tiger.
His leadership in the backline was crucial last season after coming to Punt Road as a free agent.
Riewoldt and Grimes won't hold official leadership titles this season, with the Tigers opting for a reduced group from last year's.
"Given the improved maturity of the team, we believe a five-player leadership group is a sufficient representation of the playing list," coach Damien Hardwick told the club's website.
"We are proud of the way Trent embraced the captaincy in his first year, and we're confident he will continue to be a strong leader on and off the field, along with Brett as vice-captain.
"Troy Chaplin's inclusion in the leadership group highlights the impact he has had on the group in a short period of time, and is a reflection of his strong character, and qualities as a person, which were things we identified when we recruited him to the club.
"We want to develop a culture that encourages every player on the list to be a leader in some way, and our challenge as a football club is to help them do that."
Riewoldt is set for a role slightly higher up the field this season, while Grimes is hoping for his first uninterrupted season since he was drafted.
The 22-year-old has played 26 games in four years, with persistent hamstring injuries derailing him early on and a fractured foot hampering him in 2013.
He missed last week's Australia Post Community Camp in Warnambool because of hamstring tightness, but had put together a decent pre-season before that.
Cotchin took over from Chris Newman as captain last year after the veteran stood down following four years as skipper.
Newman elected not to be in the 2013 leadership group and will again remain outside the official structure this season.
The Tigers will play their first NAB Challenge match on Friday night against Melbourne at Etihad Stadium.