Sunderland have failed to keep a clean sheet in any of their last 17 matches.
However, Allardyce is worried that he has put too much pressure on his side, by continuously talking about the importance of defending.
“It [keeping clean sheets] would be the foundation, but we don’t do it very well and that’s been very disappointing for me as the coach,” he said.
“It doesn’t stop me from continuing to work on it on the training ground, but perhaps I shouldn’t have mentioned it so much because you can make people a bit paranoid if you keep going on about it.
“But we’ve been working on it, and we were doing so again on the training ground yesterday.”
Sunderland have kept just three clean-sheets all season, and their struggles at the back have proven costly.
Allardyce’s side have thrown away leads in the latter stages of matches recently, and that has proven damaging for their survival chances.
Sunderland are currently stuck in the relegation zone, with time running out for them to make it out of trouble.
The Black Cats have just eight league games remaining, and as things stand they are two points adrift of safety.
Sunderland’s next match comes against West Bromwich Albion at the Stadium of Light tomorrow.