Swansea head into a crunch clash with fellow strugglers Sunderland at the Liberty Stadium on Saturday with statistically the worst defence in the Premier League.
The Welsh club have conceded a league-high total of 31 goals - 19 of those coming in the seven games Bradley has overseen since succeeding Francesco Guidolin at the start of October.
Swansea returned to the bottom last weekend after a 5-0 mauling at Tottenham, but victory over Sunderland would move them above David Moyes' Black Cats and even out of the relegation zone if other results were to go in their favour.
But Swansea have conceded nine goals in two games - the Spurs debacle coming on the back of an incredible 5-4 home victory over Crystal Palace - and Bradley said: "We have to defend better in all areas.
"We're not going to survive if we continue to concede that number of goals
There have been moments along the way where I think we felt all right and saw a small step in the right direction.
"But that has to be more consistent because we have been conceding all different kinds of goals."
Former United States boss Bradley has been heavily criticised by Swansea supporters on radio phone-ins and social media this week, with many calling for another managerial change to prevent relegation.
But Swansea chairman Huw Jenkins told talkSPORT the club need stability and not another sacking, and Bradley says he is already focusing on the January transfer window with the signing of a new defender a priority.
"We can use a defender, a guy we can count on week in and week out," Bradley said
"And we need players who can hit the ground running and make an impact
"We do not have the luxury of letting guys have three or four months to adjust to the Premier League."
Swansea's defensive frailties will certainly be tested by in-form Sunderland striker Jermain Defoe, who has eight goals for the season after scoring four in his last five games.
Defoe claimed a hat-trick in Sunderland's 4-2 win at Swansea last season and Bradley knows the former England forward well
Defoe was a Toronto team-mate of his son Michael.
"Everyone knows Jermain has made a career out of a savviness in the way he moves and lethal finishing," Bradley said.
"He still finds those little cracks and chinks and, if allowed, scores goals.
"Sunderland have other ways to attack and they can choose to be direct with (Victor) Anichebe
"But that is often done to make room for Jermain
We must recognise where he is and close him down, because he is a striker who lives off the tiniest spaces
"We all know how big this match is, our version of a cup final
We've had a few of those already, but it feels like the biggest one."
Source : PA