Manchester United produced a memorable comeback to defeat Braga 3-2 last night, with Javier Hernández's 75th-minute header sealing only their second win from a two-goal deficit in the Champions League. It left Sir Alex Ferguson again bemoaning his side's defending after the Portuguese club required only 80 seconds to open the scoring.

"It's been the story of our season," the United manager said, "starting badly and losing goals and fighting back to rescue games. It's the front players who are doing that for us. Some of our football was terrific tonight, some fantastic football. We created a lot of chances. But it is a concern we are losing goals.

"We came through OK. I can't understand our defending. We made it difficult for ourselves [but we] got a result most people wouldn't have expected when we were two-nil down. Credit to the players, they don't stop."

United have now trailed in eight of their 12 matches this season. "I can't get to the bottom of it," Ferguson added. "If you analyse all the goals we are losing, they are all different types, a cross and then a cutback and players free in the box tonight. It is difficult to put my finger on it. We are certainly not getting good starts to games, that's for sure.

"It's the home games we are losing the goals so early. Away from home it is not a problem in terms of early goals. We will sort it, I am sure of that."

Ferguson rested Rio Ferdinand, who was an unused substitute on the night, and Patrice Evra, with the left-back omitted from the squad. With hindsight, might the Scot have selected them? "I think we did the right thing. It wasn't Michael Carrick's fault for the first goal," he said of United's emergency centre-back. "He did his job well. You have to look at the big picture, Rio at his age, [with a] big game against Chelsea on Sunday, Chelsea on the Wednesday [in the Capital One Cup], Arsenal [the following] Saturday, we have a massive programme and it is important to utilise the squad.

"OK, at the moment with [Nemanja] Vidic out and [Phil] Jones and [Chris] Smalling not available then putting Michael back there is not the best, but he did his job well."

The only previous occasion United reversed a two-goal deficit was against Juventus in 1999, when a Roy Keane-inspired United won by the same score to reach the final of the competition, which they went on to win.

Against the Portuguese side, Ferguson's team first went behind to an Alan goal, the Braga captain then doubling his side's advantage after 20 minutes.

The first of Hernández's two headers came on 25 minutes before Jonny Evans scrambled the equaliser just past the hour. Then the Mexican sealed a notable win, to make it maximum points from three matches.

It also gave Hernandez a third goal in four starts. "He is improving all the time," Ferguson added. "He trains magnificently and has great enthusiasm. I must say he's got me thinking. He is a fantastic trainer, practises all the time and has given me a problem. That's good. His goal ratio for us is fantastic. The second, he has bent his run behind the defenders – [it was a] great ball from [Tom] Cleverley but his movement was terrific.

"I have got him, Wayne Rooney, Robin van Persie and Danny Welbeck [to choose as strikers], and I don't know what to do with them. I've been saying it for the last few weeks – our forward play has been getting us out of hole."

Of Shinji Kagawa, who was replaced at half-time, Ferguson added: "He has twisted his knee. We will assess it. It is too early to say if there is any damage or not." The goalkeeper Anders Lindegaard has injured a thumb, moreover, and "should be OK in a week's time".