Stuart Lewis sentenced the Shrimps to just their fifth defeat on home soil this season in a forgettable match and Bentley was stunned at the level of performance.
He said: "I'm shell shocked to be honest because we were terrible. It was definitely the worst performance I have seen since I took over and I feel really flat. It was an awful game of football full stop and I feel sorry for the fans that came to the game and will say sorry to them for what they saw.
"The conditions were poor and the pitch was an absolute killer for us as we couldn't play the football we wanted. Because of that we had to show a bit more guile to try and create an opening but we didn't do anything and we have to be much better than that.
"The game was always likely to be won or lost on a set piece and that is how it proved and I want much more from my lads because even though we have 52 points we are not mathematically safe and need to show far more desire and creativity than we did here."