Soccer:Alex Ferguson has no idea what is causing his Manchester United side their defensive headaches. For the eighth time in 12 games this season United found themselves behind, on this occasion against Braga at Old Trafford last night.

Thanks to two goals from Javier Hernandez either side of Jonny Evans’ second in three games, United were able to roar back for a 3-2 victory that almost certainly guarantees a place in the knockout phase of this season’s Champions League.

However, with Chelsea to come twice, and a Premier League home game against Arsenal before the rematch with Braga in a fortnight, Ferguson knows unless he finds a solution, his team could be in massive trouble.

“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.”

Despite his goal last night, Evans is one those who will be tasked with putting things right at the back and the Northern Ireland international is eager to do just that.

“It’s happened quite a lot,” he said. “It is becoming a bit of a habit but it’s something we have to eradicate as we don’t want to give ourselves that kind of deficit at the start of games. We need to get better starts in the future.”

At the other end, Evans thought he had blown his chance of extending his goalscoring streak. After taking 119 matches to net his first United goal against Wolves last season, he opened his account this season against Newcastle before the international break before scoring against Braga last night.

Instead of the plaudits, however, Evans came close to taking the brickbats, for when van Persie’s second-half corner was flicked on by Michael Carrick, despite the ball dropping perfectly for the 25-year-old, he could only take a fresh air swipe at it. Only after Braga made a hash of trying to clear it did the opportunity arise again. Even then, Evans could not be certain whether he got the final touch.

“I was devastated when I miskicked it but I turned around and managed to get a bit of a toe on it,” he said. “I didn’t know how it went in and thought it might have been an own goal or something but I’ve come in, seen it back on TV and know I got a touch on it.”

United paid for resting Rio Ferdinand, who was replaced in central defence by Michael Carrick. The England man was at fault for Braga’s second when he was turned far too easily by Eder, who provided Alan with the easiest of finishes.

At that stage, United were already trailing as Alan had opened his account after just two minutes. But Hernandez prompted a fightback and after pulling a goal back from close range, he also bagged the winner 15 minutes from time after he got on the end of Tom Cleverley’s far post cross.

“The boy is improving all the time,” Ferguson said of the Mexican. “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.”

It was the first time United had recovered from two goals down in a European game since they beat Juventus in the 1999 semi-final, although Ferguson could do without the omen. “I would rather be without it,” he said.

The victory did not come without its pain either as Shinji Kagawa was forced off with a twisted knee. In addition, Anders Lindegaard has a thumb injury that will prevent him from being involved in Sunday’s title clash with Chelsea at Stamford Bridge.

Already four points adrift of Roberto Di Matteo’s side, defeat for the Red Devils is out of the question.

Although they did emerge victorious in a Champions League quarter-final two seasons ago, United have not managed a league triumph at Stamford Bridge since 2002. And for all the disappointment at Chelsea’s surprise defeat to Shakhtar Donetsk last night, Evans knows nothing will come easily to the Old Trafford outfit.

“We have had some great battles with them down the years, but they have changed quite a lot very quickly,” said Evans. “You can see that from the way they have been scoring their goals this season. They scored four again at the weekend so it’s going to be a tough game and our record down there has not been great over the last few seasons, so that makes it a bit harder still.”