Mikel believes it is difficult for players being in and out of the side.
"You can say some of us are a bit tired," said Mikel, who in January won the African Nations Cup with Nigeria.
"We knew it was going to be tough with the run of games that we have, so we were kind of prepared for it. The manager is doing his job by rotating the team as well, so it keeps some of the players a bit fresh going into every game.
"It is hard to maintain that level. You want to keep that rhythm going, that level going, and when sometimes you have been rested and you come back, you kind of lose that rhythm.
"It is hard to take, but you know it's something that everyone has accepted since the manager came in. He said from the start that he was going to rotate the team, so we have to get on with it.
"It's tough but, hopefully, if we can go through this period of games, still in the top three or four, we are going to be pleased with what we have achieved.
"The most important thing is the team. If the team keeps doing well, keeps winning, most especially towards the end of this season now, we need everyone, we need to keep playing and winning games.
"If the team keeps doing that then I am very happy."