Alex Ferguson insists his Manchester United side cannot continue mounting "rescue jobs" if they want to wrestle back their Premier League title.

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."