Rovers are just four points above the relegation zone with a month of the season remaining and have not kept a clean sheet for six matches.
However, with points at a premium Allardyce believes not conceding goals could be the key to their survival, starting against Wigan this weekend.
"We have to look to defend very well indeed and get as many clean sheets as possible while looking to get the one goal to win us a game," he said.
"Our front men (Jason Roberts and Roque Santa Cruz) are missing and our chances of scoring are limited without them.
"We have to concentrate on that all-important clean sheet. In our situation at the moment anything you get is another point towards the total you want to achieve, although three points against Wigan would ease the pressure on us."