Local fans turned on their players during the 1-0 loss.
"The system doesn't count for very much. We have to improve individually and give much more to the team," slammed Petkovic.
"We are still tired and lacking the right mentality. This really isn't good enough and some players have to give more. I want players who give their heart and soul. We've got to work harder and anyone who doesn't understand that simply won't play.
"Will we bring in different players on the transfer market? I am focused on working with the squad I have."