"The pitch was fine. The score was achievable playing in the second innings and at half time we were pretty comfortable. I must say the batting was below standards, considering the (batsmen's) experience," said Fleming at the post-match press conference.
"Some of the dismissals were truly out of character. It is not acceptable," he added.
Chasing a modest total of 149, CSK skipper Mahendra Singh Dhoni almost won the match for his side with a breathtaking 51-run knock off 26 balls but his dismissal in the first ball of the final over scripted Mumbai's sensational win.
"If you try and analyse it, may be this is the first game in IPL 6. Coming from Test series, there may be confidence or over confidence. Mumbai bowled well and they did enough in putting pressure on us. We do not like to see our batsmen out of character.
"It is not about harsh words. It is a reality check. To be honest, I am not a coach to blow up things but I was disappointed on the nature of the dismissals. We did not deserve to win this game. We are hoping we will perform better in the next games," he said.