Manchester United must prove Arsenal victory was no one-off once to return to the Champions League last-16

United will qualify for the knock-out stages for the first time in four years unless catastrophe strikes against CSKA Moscow on Tuesday night

Manchester United won away from home to a top club for the first time under Jose Mourinho (Getty)

Michael Lang's late winner for Basel a fortnight ago had many of those in the St Jakob's Park press seats searching for a pocket calculator.

On a night when Manchester United required just a point to progress to the knock-out stage, the 1-0 reverse was a surprise to say the least and worse still, it opened up a raft of permutations ahead of the final Champions League group game.

Defeat by seven goals or more against CSKA Moscow tonight will consign Jose Mourinho and his players to the Europa League for another season. A draw, however, will still be enough to win Group A outright. United could even lose by four to their Russian visitors and still finish ahead of both them and Basel.

The full list of permutations is a complex one but, as often with these things, it can be boiled down to a single truth: barring a barely-believable collapse, United will reach the last 16.

That, in itself, will be worth celebrating. It will be only their second appearance at that stage of the competition since Sir Alex Ferguson's retirement and as records go for the highest-grossing football club on the planet, it is a poor one.

This current United side, however, looks like it could be capable of making up for lost time. It is certainly still flawed in areas and often relies upon the qualities of one or two important players in order to secure results, but a quick survey of European football's present landscape bring up a lot of big clubs with similar problems.

Take three fellow super-clubs who, unlike United, do not currently top their Champions League groups. Real Madrid, Juventus and Bayern Munich could await Mourinho's side in the next round. All three have consistently progressed to the latter stages of this competition in the last five years, but this season, they have also shown evidence of vulnerability.

If United are drawn against any one of the group stage's other second-placed clubs, a quarter-final place should be regarded as a minimum requirement. Shakthar Donetsk, Sevilla, Porto and Roma are all talented sides, but United would be favoured to come out on top.

And if a spot in the last eight would constitute success, anything beyond that would make for an excellent return to Europe's elite competition. Yes, three of the leading favourites - Manchester City, Paris Saint-Germain and an out-of-sorts Barcelona - look a cut above this United side, but the point is not that United would beat them. The point is that over a two-legged tie, they could.

Much of that is down to Mourinho, who reminded us “Einsteins” on Saturday that even if his big-game approach has its faults, he has not totally lost his ability to rock up in a rival's backyard and best them. The victory at Arsenal was a side fulfilling their manager's instructions down to the last letter. “I have to say that my players deserve all the great words. I don’t know so many more in English,” he said post-match. “Amazing, phenomenal, fantastic, and deserved the three points.”

The win was Mourinho's first away from home to one of the Premier League's 'top six' in more than three years though, and his wait for one in the Champions League knock-out stages stretches even further back – to Old Trafford in March 2013, no less. With just one semi-final appearance in four years, his recent record in this competition is a poor one.

Barring catastrophe on Tuesday, he will have the chance to improve on it. Combine United's steady progress with their manager's specific talents, then consider how open the road to Kiev looks this season. Once they reach the knock-out stage, there is no reason why they cannot be competitive. Come February, it will be up to them to prove that the Emirates result was no one-off.