Manchester United manager Louis van Gaal has said that his side's defeat to Wolfsburg in the Champions League "is difficult to understand".

The Premier League giants have been eliminated from the competition after losing 3-2 in Germany, with two goals from Naldo and a Vieirinha effort helping the Bundesliga outfit to victory.

However, while Van Gaal was disappointed with the goals that his team conceded, he was also left frustrated after United had a goal disallowed just before half time when Juan Mata was adjudged to have been interfering in play from an offside position as a cross from Jesse Lingard found the far corner.

The Dutchman told reporters: "The result is difficult to understand. I am happy we have scored and not happy we have two times in two minutes given the goal away. I have to analyse why that is happening. Normally we are very good in that aspect.

"I have said in advance that this is a tight group and you see that in the results that we have made - and also our competitors.

"I have to say that we were not so lucky in a match today, with the decision of the referee, and also in the first match too. When the group is tight that kind of decision can decide whether you go through or not."

After finishing in third place in their group, United will feature in the Europa League in February.