The Nigeria midfielder said: "We're all just shocked. Last week we lost not playing well against Sunderland but this week we played well and created a lot of chances. We are all really really devastated, we are all really sad about the Birmingham game. We know how well we controlled the game but that's football."
Mikel said Birmingham were lucky to win after Lee Bowyer scored in the 17th minute at St Andrews.
Mikel added: "They had one chance and it wasn't even a chance - it was just a long ball and a knockdown. It's just crazy and we don't know what to say about it."