The former Hibs and Scotland attacker was reflecting on his career as he spoke to Simon Ferry on Open Goal.
Riordan spent two seasons at Parkhead after moving from Hibs in the summer of 2006, but he found his opportunities limited under Gordon Strachan.
After failing to convince his manager that he deserved a regular run in the team, Riordan returned to Easter Road.
Asked if he believes he would have bagged 30 goals a season, Riordan answered: “Aye, I do. The amount of chances you get. If you look at the likes of [Henrik] Larsson, he got about six or seven chances a game and he’d take at least two.
“I’m confident enough that I would take at least two chances if I had six or seven shots.
“If you’re a Celtic player you should be hitting 20 goals a season, no matter what type of striker you are.”