The Brazil international saw a protracted transfer saga brought to a close when completing a big-money switch to Catalunya in the winter window of 2018.
Barca had been pursuing his signature for some time and were eventually able to talk those at Anfield into relaxing their stance and parting with a prized asset.
Riera insists that is not for a lack of trying, with time still on the 26-year-old’s side.
The former Liverpool and Spain winger told Goal when asked if Coutinho took the correct career path: “Yes, he came from a very big club like Liverpool and went to probably the best club in the world right now. Not everyone has that opportunity.
“If we talk about performance, we have to be clear that he is a player that can always be selected. In the end, if they demand more, it is because they know that he can give it.
“They have a lot of quality and he can do better despite being a very important player. He is the first one that wants to play, one hundred per cent.”
Coutinho’s next opportunity to impress could come against his former club, with Liverpool due at Camp Nou for the first leg of a Champions League semi-final on Wednesday.
Riera is expecting a competitive encounter between two European heavyweights, but believes Barcelona will secure an advantage to take with them for a return date at Anfield.
He added when pressed for his prediction: “It's hard to say, but if Barcelona are able to apply their game then they they will get it right.
“A 2-0, or maybe a 3-1 would be a good result but I do not see many goals in the first leg. I do not think they're going to go crazy.
“We'll see a quicker game in Liverpool, and at Anfield I do expect more goals. There may be a draw there with more goals and finally Barcelona will go through.”
The claims of the newly-crowned La Liga champions to a final berth are aided considerably by the presence of Lionel Messi, with Riera conceding that it would be pointless for Jurgen Klopp to try and piece together a plan to stop the mercurial Argentine.
He added: “All the coaches have tried it.
“He’s an incredible individual but I think it's a mistake to look only at him.
“Barcelona has the ability to move the ball very quickly and find the free man. It will not always be Messi, but he has the ability to make things happen around him.
“Everyone will have to pay attention to their defensive duties, but I have no doubt that Liverpool will look to close off the space down the middle.
“I think the key will be the pace of the game. If Liverpool are not comfortable, Barcelona will have a lot of chances to win.”