Three decades ago, when Manchester United were about to face Galatasaray, they were greeted with banners declaring: “Welcome to Hell”. Thirty years on, United may have found hell: not in Istanbul, but in Manchester. A second home defeat in four days has sent them spiralling into crisis.

So much for Raphael Varane’s assertion that they can win the Champions League. At this rate, bottom of the group, beaten six times in all competitions already this season, they may not even be playing in the Europa League after Christmas.

A 3-2 loss came courtesy of their own failings: of disastrous defending, of the indiscipline of the sent-off Casemiro, of the poor team selection by Erik ten Hag. Even a colossal contribution by Rasmus Hojlund, who scored twice, had another goal disallowed and provided a chance that Bruno Fernandes really should have taken, was obscured by United’s ineptitude.

It says something that Davinson Sanchez – that Davinson Sanchez, the former Tottenham centre-back – registered two assists. The second encapsulated United’s haplessness. The Colombian’s header from his own half released Mauro Icardi to run through a shot over Andre Onana, a goalkeeper with a marked reluctance to save any shots.

It was rendered easier because Icardi, escaping behind United’s centre-backs, was played onside by the out-of-position makeshift left-back Sofyan Amrabat. It was a wretched night for United’s full-backs: Amrabat was partly culpable for Galatasaray’s second equaliser as well when Bans Yilmaz raced into space behind him before finding Kerem Akturkoglu to finish.

Galatasaray’s first goal – scored, with a certain inevitability, by Wilfried Zaha – could be put down to Diogo Dalot. Outmuscled by the winger as Sanchez’s long ball landed in front of him, he allowed Zaha to hook in a shot that bounced over Onana. It was not the first time United had grounds to rue their mismanagement of Sir Alex Ferguson’s last signing. Zaha played four times for them and has now scored four goals against them.

Yet Zaha, too, was demoted to a supporting character in the broader tragicomedy of another display of United haplessness. They were a team who were twice reprieved and immediately conceded. Akturkoglu was guilty of a glaring miss when Onana spilled the ball; United let him score instead shortly afterwards. Icardi drilled a spot kick wide after Casemiro, in his final contribution, chopped down Dries Mertens. He was soon on the scoresheet anyway.

And for Casemiro, cautioned in the first half, a third red card of a brief United career highlighted how his lack of mobility and their shambolic tactics are dual problems. The Brazilian cannot get to the ball as quickly as he used to. United leave him exposed and, after Onana gave the ball away, he slid in on Mertens.

For United, defeat to Bayern Munich by a one-goal margin may have had a certain respectability, much as he 4-3 scoreline in Germany flattered them. A loss at home to Galatasaray has no such sheen. The Turkish champions struggled past Molde in a play-off and went 2-0 down to FC Copenhagen two weeks ago. They brimmed with spirit and showed quality in attack, but the architects of defeat were United themselves.

Ten Hag has to take his share of the blame. Picking Hannibal Mejbri backfired and not merely because the youngster, who was hauled off at half-time, contrived to block a goalbound shot from Mason Mount. Yet to focus on the rookie would be overly harsh: senior figures were found wanting.

And the one player who should escape censure was United’s youngest starter. Hojlund was outstanding, taking his tally to three goals in two Champions League games, twice putting United ahead. They should have led earlier, Fernandes miscuing a shot wide after the Dane wriggled clear to cross.

Then Casemiro hooked a pass over their defence, Marcus Rashford chased it and lifted in a cross and Hojlund accelerated past Davinson Sanchez to head it in.

The ubiquitous Colombian had a part in his second, too, slipping as the £72m man sprinted half the length of the pitch to lift a shot over Fernando Muslera. United could rue the moment when Rashford, in trying to provide Fernandes with an open goal, under-hit a pass and allowed Sacha Boey to intercept. Often criticised for his decision-making, this time Rashford’s execution was the issue.

But they had far greater problems, lacking control or cohesion, wrenched open, taking the total of goals conceded in Europe this season to seven already.

They have horrible memories of visiting Istanbul three decades ago and of being eliminated from the Champions League by Galatasaray. A return at the end of November could come with a similar fate.

And a comparison would emphasise their failings: in a year when Manchester City won the Champions League in Istanbul, Manchester United could exit it there.