The Blues suffered their first home Champions League group defeat in more than a decade as they lost 2-1 to Basel on Wednesday.
Mikel admits that Chelsea need to step up their performance, but is not worried due to the quality they have within their squad.
"With the kind of players we have, with the calibre of players we have here, I don't think we should be afraid of anyone," he said.
"But if we play the way we did against Basel, we have a chance of losing to anyone we play.
"We have to go back to training now and look at the things we have done wrong and try to put it right.
"It's disappointing. It's really, really bad. I mean, it's a very bad result for us. We knew the kind of team we were playing against.
"We knew how good they are on the ball and what they can do when they have the ball.
"The manager spoke about how we had to put them under pressure from the first half, the first minute, and then they don't have a chance to win here.
"But we didn't do that, it's very disappointing. And it's very disappointing to our fans, the way we lost the game. Coming from another defeat at Everton, we wanted to use this game to put things right but we didn't.
"Individually we didn't turn up. Next game we have to put things right and put ourselves in the position of qualifying from this group."