Former Hibs hero was as good as Karim Benzema and should have earned a big-money move claims ex-teammate Steven Thicot.
The pair became friends as Riordan made his return to Easter Road following a disappointing stint at Celtic.
Frenchman Thicot, who played alongside Real Madrid's four-time Champions League winner at international youth level, insists he was taken aback Riordan's ability.
He reckons the journeymen striker, who turned out for Brechin, York and Edinburgh City in the later stages of his career, should have earned a bumper contract in the Premier League.
Thicot told the Talkin Fitbaw Podcast: "And with the ball at his feet, I played with Karim Benzema and stuff but like to score a goal, his ability, wow.
"Many times I was like 'How can you not play in England?' I was like, 'Derek, please run a bit more, you should be a billionaire man!'
"He was gifted, he made it through the Academy and stuff like that and sometimes you maybe realise when it’s a bit too late and then I'm not going to be able to talk that much because sometimes there's personal issues.
"It doesn't mean that there's a problem in your life but maybe there are things that we don't know that are bothering you.
"I'm very pleased to be able to say that I played with Derek Riordan in my career, that's for sure."
