Manchester United were given a taste of what could have been as Harry Kane helped Bayern Munich to victory over Erik ten Hag's struggling side in a high-scoring and eventful Champions League opener.
It was no secret that the Red Devils would have liked to have signed Kane from Tottenham in the summer, but instead, England's captain and record goalscorer opted for a career in Germany that has begun in stellar fashion.
At the Allianz Arena on Wednesday, the 30-year-old claimed both an assist and scored from the penalty spot - after a VAR check to rule Christian Eriksen had handled in the box - to take his tally of goals this season to five in five games in all competitions.
It was a timely strike from Kane too as it came just after Rasmus Hojland had scored his first United goal to make it 2-1 early in the second half and give his side some hope of a result.
Before that, goalkeeper Andre Onana had undone a disciplined start from the visitors with a shocking error to allow Leroy Sane's drive to slip under him and find the net in the 28th minute.
Four minutes later, Serge Gnabry struck low and accurately inside the far corner to make it 2-0.
It is to the visitors' credit that they came out swinging to try and make a contest of it but their current fragility and lack of options from the bench as a result of numerous injuries undermined their ability to compete.
Casemiro showed dogged determination to smuggle a second in for United to give them a glimmer of hope but Mathys Tel snuffed that out by hammering a Bayern fourth high into the net in added time.
United were not finished, with Casemiro heading home Bruno Fernandes' free-kick from close range with almost the last kick of the game, but it was too late.
An opening-game loss at the six-time champions of Europe will not define the campaign, especially with FC Copenhagen and Galatasaray - who drew 2-2 earlier on Wednesday in Istanbul - both more beatable in the group, but they are now in dire need of a response to restore some focus and faith.