article_snippet.sent: Argentine £60m man Di Maria came on for Juan Mata in the 81st minute at Old Trafford Trafford .
article_snippet.sent: Fellaini headed in at the far post to give Manchester United the lead and continue Fellaini fine recent form .
article_snippet.sent: Mata slots under Joe Hart to extend Manchester United lead to 3-1 early in the second half .
article_snippet.sent: Chris Smalling headed in a free-kick to score Manchester United fourth goal in the derby .
highlights_snippet.sent: Manchester United beat Manchester City 4-2 at Old Trafford .
  
highlights_snippet.sent: Win moved Manchester United four points clear of City in third place in the table .
  