Portuguese World Cup star Carvalho told the Mirror: "These two derbies are decisive for us. If we get the six points then we will put pressure on Manchester United in the race for the title.
"We suffered a big blow when we lost to Tottenham in the Carling Cup final and, of course, we want to make up for that and show people what we are capable of.
"It was the same in the FA Cup. Some people lost belief in us and that did affect our confidence, of course.
"But if we win these two games then we will be back in the title race - believing we can win it.
"Even though we have suffered badly in the two cup competitions, we have come back strongly and fought like lions in every match since.
"We are as dangerous and as strong as ever, and determined to win a trophy this season.
"We know for a club like Chelsea it would be seen as a failure not to win a major title."