"We've been letting too many goals in and it just keeps happening," the defender told BBC Radio Cambridgeshire.
"It's the same every week so we must be doing something wrong and it would be unfair to pick on the forwards."
Posh go into the weekend's clash with Crystal Palace looking odds-on for an immediate return to League One.
They have managed just one win since the arrival of Mark Cooper in mid-November.
However Bennett says they have the chance to drag financially stricken Palace into the relegation battle.
The Eagles have been deducted 10 points after entering administration on Tuesday.
"Hopefully we can go there and make the most of their situation. We need to put more pressure on them," Bennett said.
"If we can get the three points that brings them into it even more."