Clark said: "We can take huge positives from certain parts of the game, but massive negatives from other parts of it. I need to have 18 players every time I pick a team who are willing to produce to the expectations of the club and the supporters.
"My players need to stand up and be counted and for 10 games we'll go right for the jugular and hopefully will get what we want."
Their latest setback was a 3-1 reverse against Norwich and Clark added: "I've told the players we've ended up losing a game I would've been disappointed to get a draw from, but the bottom line is that everyone in the side has to accept their defensive duties and do them better. The players haven't done that and it has cost us."