Manchester, Oct 1 (IANS): Manchester United manager Louis van Gaal has said that his players need to improve to reach the knockout stage of the Champions League.

United had a shaky start to their European campaign in Group B when they suffered an away defeat to PSV Eindhoven in their first match. But the former English Premier League (EPL) champions brought things back on track with a 2-1 victory over VFL Wolfsburg here on Wednesday evening.

Although United started the match on the wrong foot when some sloppy defending allowed Daniel Caligiuri to put Woflsburg ahead, fine performances from Anthony Martial, Antonio Valencia, Juan Mata, Wayne Rooney and Bastian Schweinsteiger allowed the hosts take control.

But van Gaal was still not not impressed and felt that United should have ensured better control over the game once they took the lead in the second half.

"After that, it was not good and that is remarkable because when it comes to keeping the ball in our possession we have done that very well in the last five or six matches.

"We have given a lot in the first half to get back in the game and maybe it was also because of the accumulation of matches in the last weeks but I cannot understand how we can give the ball away so easily," the Dutchman was quoted as saying by the Guardian on Thursday.

"We have to keep our feet on the ground and we have to improve a lot to be the top of Europe. We have beaten Wolfsburg and I am very happy about that. The players are also very happy but we have to improve and we have to know that. So I have said that to the players.

"That is why we are here, to improve ourselves so we win every game. Today we have won this game but it could have been done in a better way. We were suffering in the end. A lot of players are very tired because of the accumulation of matches. But I think the team spirit kept us in the match," he added.

United had pulled level when Mata converted a penalty after Caligiuri inadvertently handled the ball inside the Wolfsburg penalty area. Mata did well in the centre of midfield, but van Gaal asserted that the Spanish international is capable of doing better.

"I have seen Mata play better than today. I agree with you (that he played well) but I don’t agree with you," the former Holland manager said.