United have fallen behind seven times this season before going on to record wins with their latest comeback victory being a 4-3 win at Reading on Saturday.
But the Manchester United manager knows they will not be able to escape for that much longer with their charitable defending that has seen them concede 15 league goals already this season.
With the Manchester derby at the Etihad Stadium looming on Sunday, Ferguson will know his side can ill-afford a repeat defensive performance.
“I thought it would be a record score against Reading for the Premier League at half-time,” he said.
“It was unbelievable. There was some real bad defending in the first half. The worst we have been this season, absolutely the worst.
“We have to sort that out. We got battered and deserved to be but we are getting goals to rescue us all the time.
“In the first-half I said to myself it would be a miracle if we win this one the way we were defending. I’m just glad we did win it.
“It’s not a question of character. But if you make mistakes like that defending, then it’s going to be rescue jobs every week. Once again this was.”
United conceded six goals, albeit on home soil, 14 months ago to next opponents Manchester City.
It looked as though history could repeat itself at relegation-threatened Reading before Robin van Persie had the final say in the seven-goal thriller to send them back to the top of the league.
The visitors fell behind to Hal Robson-Kanu’s fine opener before normal service was resumed when Anderson and Wayne Rooney’s penalty looked to have put them in control.
But two headers from Adam Le Fondre and Sean Morrison, both from corners, would have left Ferguson fuming.
It would have also had Roberto Mancini, the Manchester City manager, sit up and take notice.
United responded, as they so often do, with Rooney and van Persie wrapping up the win in this see-saw game that saw seven goals in the first 30 minutes.
Rooney admits his teammates must heed the lessons.
“It was not good enough defending set-pieces and it could have cost us,” he said.
“We had to make sure we defended better in the second-half. The message at half time was to defend better, stay with our runners and get against them at set-pieces and we did that.
“We always believe in ourselves. Even when we went behind twice.
“It was important seeing the results earlier to get three points, regardless of the performance. And we did that. It was like a basketball match at times. I’m sure the fans were delighted watching it, but I’m not so sure you want that every week.”
Reading remain rooted in the relegation zone but manager Brian McDermott says his players will take heart from a display which fell narrowly short.
“We just have to remember where we a few years ago,” he said.
“We lost 4-1 at Plymouth and it could have been 10 that day. We were staring the second division in the face. Where we are now is a phenomenal achievement for the club. It shows how far the club have come.”