Mikel has revealed that the hectic fixture schedule has tested Chelsea's squad to the limit, but the Nigerian remains confident of a top-four finish in the Premier League.
He told The Mirror: "This season is harder even than last year when we won the Champions League, especially in the Europa League, there are more games.
"I have been here seven years, we have always played Champions League games, but it's very hard this season. We are still in the Cup, the Europa League and then in the league we are still fighting for the top four. Tottenham Hotspur have put themselves right in there, Arsenal won on Saturday, so for us we have to keep playing, believe in what we can do, and focus on ourselves, and don't think about what the other teams are doing.
"But with Spurs and Arsenal, it always changes. So we have to keep doing what we are doing and focus on ourselves. The battle for the top four has always been tough. We knew it was going to be tough, coming to the business end of the season."