The Romans were left in despair when De Rossi missed a golden opportunity to revive their Champions League hopes in the quarter-final second leg tie against Manchester United.

With the Italians needing to overturn a 2-0 deficit and the game still goalless, Roma were awarded a penalty on the half-hour mark.

De Rossi - who scored the winner from the spot in last weekend's Serie A defeat of Genoa - stepped up, only to boot the ball into Row Z.

"It was one of the most difficult moments of my career," he said. "But these are things that you have to leave far aside.

"It's not the worst because I suppose the World Cup is the most important game, but a single moment can change the Champions League, it can change a season - it could have changed the game."

Roma knew they had a mountain to climb as they faced Manchester United for the sixth time in a year - having already been defeated on four occasions.

Despite pressing and harassing their opponents, the Giallorossi found any real chances hard to come by.

And things went from bad to worse when Carlos Tevez fired home on 70 minutes to end Roma's Champions League dreams.

"Manchester United are a great team," added De Rossi.

"An incredibly strong team that have at least 20 players who are absolutely top class.

"We are also a great team and it's unfortunate that we couldn't win tonight.

"But now we have to focus on the Scudetto even though we know it will be very difficult.

"It's true that Inter aren't Manchester United but there's a lot of other factors, a lot of other teams - some of whom have a lot of motivation and some of whom have less.

"It will be difficult to beat them but it can be done."

De Rossi's team-mate Marco Cassetti is fully aware of the significance of the midfielder's miss.

But while he believes it could well have been Roma preparing to face Barcelona and not Manchester United, Cassetti is adamant his side can be proud of their performance.

"Of course the game would have changed if the penalty had gone in," he said.

"We would have qualified. It's a pity - a real pity.

"We deserved it because although it wasn't a nice game, it was a great game in a difficult stadium against an extremely great side.

"But as you know in football, the games are decided by moments where you can turn the match in your favour.

"Even though we gave a great performance we had to give even better to be champions.

"De Rossi is disappointed like anyone would be who missed such a penalty but he didn't say anything to us - there's nothing to say, these things happen.

"On Sunday he got us the goal that won us the game.

"It's a pity but only in that he didn't put us in a position to secure qualification and we had the possibility.

"But I think that tonight we have shown everyone Roma's maturity and that we have grown technically and mentally."