David de Gea
De Gea injured himself in the warm up.Getty

Manchester United manager Louis van Gaal has confirmed David de Gea will undergo a scan on a knee injury suffered in the build-up to their Europa League defeat to FC Midtjylland. De Gea limped off during the warm-up and was replaced by Sergio Romero in the starting XI, just 10 minutes ahead of kick-off.

The Argentina international was his side's best performer on the night, producing two vital saves, but a wretched team performance saw United suffer a 2-1 first leg defeat away in Denmark. When quizzed on the extent of De Gea's injury post-match, van Gaal told BT Sport: "He has a knee problem, we must wait and see. We [will] investigate it tomorrow with a scan, we can't answer that now."

United should have fallen behind when Vaclav Kadlec spurned a one-on-one opportunity against Romero, who made a vital save with an outstretched foot. 56 seconds later, Memphis Depay scored the opener, prodding home Jesse Lingard's cross at the second attempt after 36 minutes.

United rarely looked comfortable with their lead however, and Pione Sisto rifled home a fine effort just before half time to level the contest. The home side went onto find the breakthrough and take the lead after 77 minutes, after substitute Paul Onuachu shrugged off a meek challenge from Juan Mata before finding the bottom corner.

United leave Denmark with a valuable away goal, but the dismal nature of their performance was far more worrying than the result itself. "It wasn't not good enough, it wasn't an acceptable performance, the result is not good enough, it has got to be a lot better," midfielder Michael Carrick also told BT.

"We caused our own problems. We haven't played well enough, we didn't kick on after we scored. It was there for us to win, we should of won, But after a performance and result like that we are going home disappointed.

"We have a chance to make it right [at home in the second leg] and go through. It is not going to be easy, but playing at home we have to our fancy our chances of going through. We have given ourselves a tougher job that we had hoped."