Director of cricket Mick Newell says Nottinghamshire's batsman must take more responsibility after their fourth straight Championship defeat.
Newell told BBC Radio Nottingham: "It doesn't go away and some of the players need to take a bit more responsibility.
"I believe they are good enough, I didn't bring them here not to be successful players."
The defending champions led the early season table after three successive wins but have since drawn to Yorkshire and lost four straight games to Sussex, Warwickshire, Worcestershire and Lancashire.
"I never look at the top of the table until August, I have said that before," added Newell.
"But we will have to win five or six games out of the last eight, which isn't particularly realistic given the way we are playing at the moment.
"Overall we are not playing well enough as a team. Certain players had a good game and certain players didn't."