Manchester United manager Louis van Gaal has criticised his side's inability to finish off Arsenal after taking the lead in their 1-1 draw at Old Trafford.

Ander Herrera gave United the lead after half an hour and the home side created a number of chances to extend their lead in the first half.

United lost their rhythm in the second half, however, and substitute Theo Walcott forced an equaliser for Arsene Wenger's side when his cross deflected off Tyler Blackett and over Victor Valdes, who was called upon to replace the injured David de Gea.

The result all but ends United's chances of finishing third in the Premier League and avoiding a potentially difficult Champions League play off qualifier in August and van Gaal believes his side have no one to blame but themselves.

"You can say we are unlucky because it is the third deflected goal in a row and falls in our net," van Gaal told a press conference, BBC Sport report. "But I have said it is not unlucky to the players.

"You have to force luck by finishing games. We are one hour better and 1-0 ahead. You see Arsenal want to come back so you have to stick together and be compact.

"I have said Arsenal have maybe the best team but Chelsea can finish the game, which Arsenal cannot do and we can't either. That is important. This season we have only finished two games. It is a pity."

Van Gaal also confirmed that David de Gea was withdrawn after suffering a hamstring injury, which could mean the Spain international has already played his final game for the club.

The future of the ex-Atletico Madrid goalkeeper largely dominated the agenda post-match and van Gaal admitted there is now a real possibility of the Spaniard leaving.

"A transfer is a process, involving a player, a club and his present club. He has to choose. It's not easy to choose between two great clubs. He's Spanish and his girlfriend is Spanish, so we would be very happy if he stays."