Mourinho explained that Mkhitaryan was still getting used to the rigours of English football, but his frustration with the player was clear when saying last month that the Armenian had to "do more".

The attacking midfielder seems to have heeded that advice, appearing in a fifth successive United match and scoring a fine solo goal to open the scoring at Zorya Luhansk.

Mkhitaryan's goal early in the first half was complemented by a late Zlatan Ibrahimovic strike in Ukraine, wrapping up a 2-0 win that saw Mourinho's men progress from Group A as runners-up.

''He has a strong mentality,'' Mourinho said. ''He was very determined to fight against his difficult adaptation, and he's doing that in the best way.

''He worked really hard physically, tactically and the talent we know is there. The talent we knew what we were buying.

''He fought to improve tactically, he fought to improve physically, and now he is playing good in the Premier League, good in the Europa League and the EFL Cup, and now evolving a bit more happiness for him, so I'm very pleased.''

That satisfaction also goes for his side's display in difficult conditions in Odessa, securing a place in Monday's last-32 draw having emerged unscathed on a poor pitch.

Players complained of the surface being like rock as their studs clacked on the frozen surface on the eve of the match at the Chornomorets Stadium, but UEFA deemed it playable after overnight heating and two pitch inspections.

''The pitch was better today than yesterday and good enough to pay football on and we appreciate the efforts to give us a good pitch,'' Mourinho said.

''There are no miracles in this cold weather, we know it's difficult to have a good pitch, so we appreciate the efforts to give us a good surface.''

Mourinho was understandably relaxed in the post-match press conference, where he spoke of his desire for Zorya to return home, having been forced to leave Luhansk due to the political trouble in eastern Ukraine.

The United manager also praised the home support, albeit tempered by frustration at some of the antics that will no doubt lead to UEFA disciplinary action.

United fans were threatened heading to a match that was punctuated by a laser pen, flare and skirmishes, along with a firecracker that landed worryingly close to goalkeeper Sergio Romero in the first half.

''The support was beautiful and they don't need that to make it more beautiful,'' he said.

''They just make it dangerous for the goalkeeper, so they don't need that.

''The stadium was beautiful, the support was good. Manchester United fans in the top were good too, we just don't need these things.

''Maybe UEFA is not happy and maybe UEFA now takes some money from Zorya, which I think Zorya doesn't deserve.''