Back-to-back Premier League defeats by Liverpool and Wolverhampton Wanderers early this month were the latest setbacks for Mauricio Pochettino's side, but an FA Cup win over Aston Villa and 3-1 league victory over Crystal Palace on Monday has restored some belief.
Chelsea, who spent more than 400 million pounds ($506 million) during last year's close season, are 10th in the league, 13 points behind fourth-placed Tottenham Hotspur.
"The victory at Crystal Palace is worth a lot to us. Last week we defeated Aston Villa in the FA Cup," Argentine international Fernandez told ESPN in an interview published on Tuesday.
"We are changing our attitude above all, and obviously this victory gives us confidence for what follows ... Throughout the season, we've had ups and downs in the league and that is why we find ourselves a little far away of the first places.
"But there is a long way to go, we have trust in our work, in a new team, and day by day we are improving to be able to meet the objective, we want to play in the Champions League next year."
Chelsea next face Manchester City in the league before taking on Liverpool in the League Cup final.
