Video Assistant Referee causes controversy every week in the Premier League , but how are decisions made, and are they correct?
After each weekend we take a look at the major incidents, to examine and explain the process both in terms of VAR protocol and the Laws of the Game.
In this week's VAR Review: Should Arsenal 's penalty against West Ham have been cancelled? What happened with Sunderland 's overturned spot kick at Manchester United ? And why didn't Alexander Isak win a penalty for Liverpool at Chelsea ?
Arsenal 2-0 West Ham
Possible penalty overturn: Position of foul by Diouf on Timber
What happened: Arsenal were awarded a penalty in the 67th minute when Jurriën Timber raced onto a pass and was brought down on the edge of the area by El Hadji Malick Diouf