Chelsea 'Have Mental Strength'  (Sky Sports)

Cesar Azpilicueta says Chelsea’s mental strength has been as important as their new signings this season.

Diego Costa's 10 goals in 11 Premier League games and Cesc Fabregas’ midfield creativity have given the Blues a playing advantage that has seen them make an unbeaten start to their season.

But as well as the high-profile summer arrivals there has also been an increase, Azpilicueta feels, in terms of the squad’s character.

"I think we are stronger mentally now,” he said after Saturday's 2-1 victory at Liverpool. “The players who came have given us another dimension as well.

"I think you saw that. When the team was losing we were still really strong mentally.

"The whole squad know we have to fight together. Some players have more talent, some score goals, and sometimes we have to defend for them - but the main thing is we do it all as a team.

"We got it back to 1-1 pretty soon and after that did very well. Obviously we'd prefer not to go behind but that is going to happen at times.

"Over the last few games maybe we haven't played our best football and the scores have been tight but over the whole season you know that everyone can't keep playing very well and winning easy.

"We knew it would be tough here (at Anfield) but we fought so hard until the end - the aim was just to get those three points and we did.

"Last year we were so close to winning the title and this year we know it will be tough but that's what we want.

"We will see in May. We're on top of the table but that's a long way off, but we want as few problems as possible up to then."

The impact of Costa, who Mourinho believes is now over his injury problems, cannot be underestimated so far this season and he gives his team-mates the confidence they will always score.

"We're lucky to have three really good strikers. We showed it when he was out, when Didier (Drogba) and Loic (Remy) came in and were scoring," added the Spain international.

"Now he's back and scoring. He plays with high passion, he's always fighting for team, and is even after goals in training - he's a great finisher.

"If we analyse him he scores but helps so much in the team. Even in last five or 10 minutes he was pressing high and doing his job. That's great for the whole team."