The Hibernian forward earned a call-up for this week's friendly in Japan within hours of being named the Scottish Premier League player of the month for September.
His recent successes are a far cry from the dark days spent kicking his heels on the bench or in the stand at Celtic.
The forward had been regarded as one of the brightest prospects in Scottish football before his move to Parkhead went sour.
But, now back at Easter Road and flourishing in his second spell at the Edinburgh club, he wants to prove he still has the ability to fulfil his early potential.
"It was a hard time for me at Celtic," he admitted.
"I went back to Hibs and it has worked out for me. I've been doing well since being back there and my fitness is a lot better this season with a pre-season behind me.
"Things are going well for me just now. I've been showing on the pitch that I'm doing well.
"I'm glad to be back at Hibs, they gave me the chance again and it's working out for me just now."
Riordan has made only one appearance for the national team so far, in a 2-2 friendly in Austria back in 2005, and believes there is still plenty of time to carve out an international career.
"I'm still only 26 and have a good few years left in me," he said.
"So I just have to keep doing well in club football. Obviously you want to stay in your national squad, you want to be at the top level."
Asked whether he ever reflects on what might have been had his time at Celtic turned out better, Riordan added: "That's football, it either goes for you or it doesn't.
"I'm happy at Hibs just now and to be playing football again.
"I want to play football, that's what every footballer wants to do, they want to go out and show what they can do.
"I want to show people what I can do on the pitch.
"I didn't play much football at Celtic in the couple of years I was there. I am back playing football again and it's going well."
Riordan now hopes to be involved in the clash in Yokohama but admits he has no idea yet whether he will have a part to play in George Burley's plans.
"I couldn't tell you," he said.
"That's down to the manager. I'll just have to wait and see. Hopefully.
"I'm just delighted to be here, I'm delighted to be called up and, if I get the chance out here, I have to take it.
"The travel doesn't put me off. I'm delighted to be here. They will be a good side and I'm looking forward to it."