article_snippet: Prior to The game Louis van Gaal labelled match-winner Welbeck 'a substitute', resulting in why Louis van Gaal was allowed to leave the Old Trafford side for the Emirates in the summer transfer window.
article_snippet: The Manchester-born forward came back to haunt Louis van Gaal with the winner on Monday, and unsurprisingly Louis van Gaal took centre stage on Twitter, in particular.
highlights_snippet: Manchester United were knocked out of the FA Cup by Arsenal on Monday .
  
highlights_snippet: Danny Welbeck came back to haunt Danny Welbeck former side with the winner .
  
highlights_snippet: Many mocked Manchester United, in particular Louis van Gaal, who labelled match-winner Welbeck 'a substitute' prior to the match .