Hold on to your hat: Manchester United are victorious in Europe after three consecutive Europa League draws and three more games without winning in last season’s Champions League.

So a 380-day drought stretching to a 1-0 win over FC Copenhagen at Old Trafford ends courtesy of Amad Diallo, whose explosive wing play was crowned by his double. The first was a clever 50th-minute header. The second an exhibition of aggressiveness as he mugged Abdul Baba along the right, shrugged off the defender’s manhandling, then fired a shot into the left corner, via a deflection.

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As Ruud van Nistelrooy, United’s interim manager, said: “The second goal had everything in it that for me is Amad Diallo. He fought to take the ball off the Paok defender, pushed through to get the shot, and had the quality to curl it round the goalkeeper.”

But, prior to that moment, United lacked the ability to kill off Paok well before the close and cruise along in control. Rúben Amorim should know this but United’s incoming manager, if watching, will comprehend the size of the challenge to transform the group he takes over on Monday.

United’s results in continental competition this season were 1-1 against Twente, 3-3 at Porto and 1-1 at Fenerbahce. Hardly a roll of honour and when Van Nistelrooy rotated Lisandro Martínez and Matthijs de Ligt for Jonny Evans and Victor Lindelöf in central defence, and Diallo for Marcus Rashford in attack, you wondered whether three points would finally be garnered.

The first half suggested not. Razvan Lucescu configured his Greek champions in a 4-2-3-1 that was a carbon copy of Van Nistelrooy’s shape and Mady Camara, the visiting No 10, exposed a familiar faultline when running into a gap, passing, collecting later in the move, then shooting.

Camara was the Paok equivalent of Bruno Fernandes: a playmaker adept at materialising in pockets and running his team. United’s captain did this when popping up at the left angle of Paok’s area and threading the ball to Diallo, whose cross was cleared. Then came a buccaneering sequence reminiscent of a Sir Alex Ferguson vintage.

Diallo jinked about infield, fed Noussair Mazraoui, who switched the ball back into space on the right. This invited Casemiro to run on and hit an instant delivery to the far post where Alejandro Garnacho headed against Jonny’s arm, but a corner rather than penalty was Radu Petrescu’s decision. The referee – and VAR – made the same call later when Diallo went down under Baba’s challenge.

Diallo was United’s bright light. His next act was to drop the ball on to Rasmus Højlund’s head but, twisting, the centre-forward’s header was insipid. A 65% possession rate showed the home team’s dominance. As usual, the problem was execution in the final third. Earlier, Garnacho fluffed a regulation pass to an overlapping colleague in Paok’s area. Now he offered a repeat, again following a burst through an inside-left channel: this time, Diogo Dalot missed.

Paok lurked, waiting to pounce on any United slipshodness. Such as when the lightweight Manuel Ugarte was bullied around the halfway line, leading to Andrija Zivkovic hammering a dipping 20-yard effort into André Onana’s clutches.

Here was a hint that United might suffer if their profligacy was not cured. Diallo was inches from doing so when hurling himself at a Garnacho cross. But he, not the ball, ended in the goal, Baba scrambling it away.

As they headed for the break – nearly behind due to a Camara rocket that burned Onana’s fingertips when deflecting over – toothless was the report on United’s opening 45 minutes. Impotency, too, is the tale of their campaign thus far. Van Nistelrooy, a ruthless assassin when United’s striker, needed to address this when his troops trailed off for the interval refreshments.

Yet more of the same followed. Garnacho did manage to locate Dalot on the overlap this time but the latter failed to find Fernandes as he arrived in Paok’s area. Fernandes showed the defender how it is done, as United discovered ruthlessness at last. Along the left, Garnacho glanced up and tapped to his captain who chipped in a precise ball that had the excellent Diallo leaping and looping a header back across goal which wrongfooted Dominik Kotarski, the visiting goalkeeper.

Fernandes was United’s hub. Next, he created for Diallo once more with a curving through ball: the forward ran in but saw his attempt saved. United were serving up another smorgasbord of chances, but too many were spurned. Dalot blazed over, Fernandes did the same, and in between Garnacho went to ground in the penalty area under the attentions of Tomasz Kedziora and Jonny, and once more Petrescu’s judgment of no spot-kick was dubious.

Tarik Tissoudali gave United a fright near goal but his nerve failed and he unloaded a shot straight into Onana’s gloves. Soon after Diallo’s second he hurt his leg and was replaced despite appearing to be fine. United will hope so ahead of Sunday’s visit of Leicester.