Cates, who started his CFL career with the Calgary Stampeders before being traded to the Riders in 2007, has racked up 4,942 yards over six years with the two teams. He was also part of the 2007 Riders that won the Grey Cup.
But his age (32), money and his recent on-field production were among the factors that went into the decision not to offer him a contract, Taman said.
"Wes is still a good football player," Taman said. "If and when somebody needs a back, I wouldn't be surprised if he gets that chance."
Mark Parenteau and James Robinson have also been released, the team said Friday.
As well, the team announced it has signed three new import running backs: Kory Sheets, Louis Rankin and Demetrius Crawford.