Sir Alex Ferguson has admitted he does not have the answers to fix the defence frailties currently affecting his side.
Ferguson watched on as United found themselves behind for the eight time in 12 games this campaign in Tuesday's Champions League match with Braga. Ferguson's blushes were spared, however, thanks to goals from Jonny Evans and a double from striker Javier Hernandez which earnt United a hard fought 3-2 win.
The victory almost guarantees United a passage into the knockout phases of the competition and with United set to face English heavyweights, Chelsea, Arsenal and Braga again in a fortnight, Ferguson knows he must find a solution to plug the hole in his defence soon, before it costs the side dearly.
"I can't get to the bottom of it I am afraid," he said. "If you analyse the goals we are losing, they have come from throw-ins, crosses, cut-backs, all sorts, and they are finding players free in the box. It is difficult to put your finger on it, and it is a concern because it is making it difficult for us."
Ferguson took the option of resting Rio Ferdinand, with Michael Carrick providing a makeshift replacement in central defence, and it was Carrick who was caught out at numerous times in the match.
Ferguson was full of praise for two goal hero, Hernandez, with Ferguson saying the Mexican's performance was testament to the hard work he has put in off the pitch.
"The boy is improving all the time," Ferguson said."His goal ratio is fantastic and the way he bent his run for the second goal was terrific. "He is a fantastic trainer and he has given me a problem, which is good."