MUNICH -- It says everything about Manchester United's current state that Bayern Munich didn't play particularly well in their opening Champions League group game on Wednesday, but the Bavarians still scored four goals, could have scored more, and won far more comfortably than the 4-3 score suggested.

It also says everything about United's campaign so far that, after three straight defeats and four in their past five games, Saturday's trip to Burnley, who have managed a solitary Premier League point so far this season, is now one filled with trepidation.

We're not even into October and it already feels like a must-win game. Burnley are among the lowest scorers in the league, but this is a United defence that appears incapable of keeping anyone out.

For the first time since 1978, Man United have conceded at least three goals in three consecutive games, and 14 in total in just six games to start the season.

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It didn't help that André Onana, the 47.2 million summer signing from Inter Milan, made a horrible mistake for Bayern's first goal, but Man United manager Erik ten Hag should count himself fortunate that the German champions were often sloppy in the final third. They hit the post twice and several times throughout the night there were frustrated groans from the home fans after another good chance was wasted.

This wasn't a seven-goal Champions League thriller -- it was United hanging on for dear life.

"We are disappointed," admitted Ten Hag. "When you score three goals in Munich you have to take a point and you have to look in the mirror because the goals were easy giveaways.

"What you have seen on a very high level -- it was against Arsenal, Bayern Munich and Brighton, all top-level teams -- we go head-to-head but they win. In the way they win, we have to make our own luck and that has to do with determination. You make your own luck, otherwise you don't get it because no one will bring you anything in football."

No one seems to do misfortune quite like United, and this time it was Onana's turn. Bayern, who haven't lost a group stage game at the Allianz Arena for nearly 10 years, didn't need any help from the visitors, but they got it anyway.

Midway through the first half, a positive start from Ten Hag's team was undone when Harry Kane, a player many United fans think their club should have signed this summer, laid off a pass to Leroy Sané on the edge of the box and his weak shot straight at Onana squirmed under the Cameroon goalkeeper. Sane seemed as surprised as anyone to discover it had gone in as Onana lay motionless, his face buried in the turf.

"We were, in the first 25 minutes, better in the game than Munich and then that goal, it was so easy and it was not only Andre," said Ten Hag. "If you see how easy Sane was going through and that has to do with determination, you don't let players through so easy. That is the point we have to cross the line as an individual and a team to win games because it started there."

Along with the many criticisms that can be aimed at this group of players, a big one is that they don't deal well with setbacks, and again the problem surfaced.

Already this season, they've conceded twice in two minutes against Nottingham Forest and twice in five minutes against Arsenal. Here, it was two goals in four minutes when Jamal Musiala found Serge Gnabry unmarked in the box and he whipped his finish into the corner. Bayern looked disjointed for large spells of the first half, managed only two shots on target, but scored twice.

It summed up United's half that, as Onana trudged off down the tunnel, he was thrown a water bottle by a member of staff and dropped it.

There were positives in the second half, particularly a first goal for Rasmus Hojlund and a large enough show of character to allow Casemiro to score twice late on, but you never sensed United were about to snatch a point.

Bayern led 2-0, 3-1 and 4-2 and would have been out of sight had Onana not redeemed himself slightly with a couple of good saves. Kane said afterward that Bayern "lost their concentration" at the end but "controlled the majority of the game," and it was hard to argue.

In making sense of this loss, Ten Hag might point to a harsh VAR penalty, scored by Kane, following a debatable Christian Eriksen handball and a squad so thin that he picked three goalkeepers on the bench. But the truth is his team were largely brushed aside by a Bayern side still trying to find their flow.

United, meanwhile, are left to head to Burnley in search of a spark to jolt their season into life.