Barcelona coach Luis Enrique said the opportunity to become the first team to defend the UEFA Champions League is a "wonderful stimulus" and clams his side have to be considered favourite for the competition.

The Catalan side opens its European defence against Luis Enrique's former club Roma on Thursday (AEST), just over three months since dispatching Juventus in last season's final.

Barca has made a 100 per cent start to its3 domestic campaign and Luis Enrique is hoping it can transfer that form to European competition, ending with further success in Milan in May.

"No, it is not an extra pressure, it's a wonderful stimulus," he said. "It's wonderful for the team, for Barca and for all Barca fans. We know it's very difficult and that nodody has ever done it but we'll try to do it.

"It's not pressure, quite the contrary. It's something of a cliche but if we're favourites because we won the league we have to be favourites for the Champions League because we are champions.

"Once the ball starts rolling there's no such thing as a champion but 32 teams who all want to be champion.

"Until it starts, all respect should be given to the previous champions, which is us."

Enrique endured a difficult season at Roma before resigning in 2012, crashing out of the Europa League in the qualification stages before finishing seventh in Serie A.

"I feel a little bit older and I think it's been a normal process in a manager's career," he added.

"Coming here reminds me of positive things, it was a difficult year but my memories are positive. I've always said that regardless of memories, tomorrow is an important game.

"I have no-one to blame, it was my decision. I explained why I left but I don't really remember that well. I had my own things to worry about."