The 24-year-old, joined Liverpool from Deportivo La Coruna for £2.5million, on the last day of the transfer window.
The full-back said: “We are not that far behind Chelsea and United, so the title is still possible.
“I’m not scared of the task ahead. I’ll enjoy working with the great players in the Liverpool dressing room.”
He continued: “It is an important step in my career to come here, the players in Spain talk a lot about what they see of the English game on TV and the pace and skill shown.
“That is what I have to learn. The game is much faster than in Spain, and I am looking forward to coming to terms with that.
“I do not feel it will be too much of a problem. There is speed and also a more physical game, but maybe that will help me as a defender because more tackles are allowed here that would be penalised in Spain.
“And I am also looking forward to the derby. I have experienced such games in Spain and I know how important they are to the people and the city.
“This is a unique opportunity. It feels great to join a club with such history and fantastic support and superb players and a very good manager.
“Rafa made a great reputation for himself in Spain and the team he put together at Valencia. Coming to work for him is wonderful for me because I believe it will make me a better player.
“In Spain, Liverpool is known as the biggest and best club in England and that is because of the history and the trophies won in the past. This has been added to by what Rafa has achieved here.
“And of course there a lot of Spanish players in the ranks now, so that will help me.”
