Life is sustained not just by what it is but by what it might be; if we weren’t continually hoping for better, how could we carry on? And the tease works just as well when watching sport, a generally disappointing activity that costs time, money, energy and patience. We keep coming back, though, mainly because that’s what we do, but also because it gives us a shot at seeing the most incredible earthly event on any given day. Your sunrises, your sunsets and your newborns are all very nice, but at its best, sport is the best, and yesterday that meant your Henrikh Mkhitaryans.

A particular joy of football is the infinite number of ways there are to get the spherical thing into the rectangular thing. Even so, most brilliant goals are riffs on eternal themes, but every so often we get a Roberto Carlos against France or a Ronaldinho against Chelsea , recalibrating reality to remind us that we haven’t seen it all.

And it reflects not just skill but character. After joining Manchester United in the summer, Mkhitaryan began the season as a substitute, a move which seemed to reflect little more than United’s comparative strength in wide attackers – and away to Hull City, he still catalysed an onslaught that brought an injury-time winner.

Next came the Manchester derby, a match which Mkhitaryan started though he’d picked up a knock playing for Armenia while, on the opposite wing, Jesse Lingard, returned after a month out. Remarkably, both were off the pace, subbed and criticised afterwards; curiously, José Mourinho was less loquacious in explaining how either were meant to get the ball given the midfield mismatch that was Marouane Fellaini and Paul Pogba against Fernandinho, Kevin de Bruyne and David Silva as City won the match 2-1. But the blame was set. Lingard vanished for two weeks and Mkhitaryan for two months, deemed ill-prepared for the harum-scarum of the English game.

This is not unusual, there was just little reason to expect it in this instance. Mkhitaryan grew up in Armenia, played for two teams in Donetsk, and then moved to Borussia Dortmund; we can probably assume that he has a solid grasp of cold, rain and grime. Moreover, he arrived at the top of his game and in his physical prime, which made Hull look a more telling cameo than City.

While he acclimatised, United floundered, dominating some games, disappearing in others, and struggling to score in nearly all of them. Apparently, a man directly involved in 49 goals the previous season had nothing to offer against Stoke City and Burnley, omitted in favour of Memphis Depay. Or, put another way, Mourinho’s policy of antidisestablishmkhitaryanism didn’t sit right, reminiscent of earlier problems with Arjen Robben, De Bruyne and Eden Hazard.

Then, at the start of November, Mkhitaryan appeared off the bench away to Fenerbahce, but despite the uniform awfulness of United’s performance, he was left out of the next two games, by which time he had played just 134 minutes of a possible 1,710. For a man who arrived as the Bundesliga player of the year, the frustration of peak months wasted cannot have been easy to take.

Eventually, though, Mourinho was convinced – coincidentally, at a time when he had run out of alternatives and was desperate for a win. So Mkhitaryan started at home to Feyenoord and was superb; it was almost as though he could have made a difference all along, not that Mourinho had calculated precisely the right moment to unleash him.

Still, he was left on the bench for United’s home Premier League draw with West Ham, returning to the starting XI for the EFL Cup tie against the same opposition. It took him all of two minutes to backheel Zlatan Ibrahimovic through for the opening goal in a 4-1 victory, and then, after a patchy but largely impressive display against Everton, he saw off Zorya in the Europa League and Tottenham with a pair of dazzling finishes, before getting injured again.

Returning against Sunderland, Mkhitaryan was introduced after an hour and almost immediately, broke with the ball in the inside-right position. Allowing it across his body as he moved towards goal, at the very last second and when it no longer looked possible, suddenly it was gliding back the other way to put Ibrahimovic in; this time, he missed. The pass, though, with its delay and disguise, encapsulated Mkhitaryan.

So it was that with four minutes to go, Ibrahimovic pulled on to the right wing and Mkhitaryan bustled into the middle. Uncharacteristically, he was ahead of the play as the cross came in – “offside”, some have said – but before the ball arrived, he somehow decided what to do, adjusted his feet, inclined his body and dived forwards as it passed behind him, flinging a leg over his back to place a finish into the far corner with the outside of his right heel! It is hard enough to describe, never mind execute.

In England, the moment of celebration is different to elsewhere, the squeak of “Yes!” not as primal, guttural and full as the roar of “Gol!” But presented with something it had never seen before, Old Trafford produced something closer to the latter, a collective “Ohhhhh!” of belief and disbelief, of ecstasy and community. It was the sound of a better life.