Manchester United manager Louis van Gaal reiterated his call for the introduction of a video referee after his side prevented Leicester City from claiming the Premier League title with a 1-1 draw at Old Trafford.
Anthony Martial fired United in front early in the game but Wes Morgan levelled with a header, before Danny Drinkwater was shown a second yellow card in the closing minutes for pulling back Memphis Depay on the edge of the penalty area.
United's players protested against Michael Oliver's decision to give a free-kick, insisting the contact was inside the box, but Van Gaal stressed how hard it was for the officials to see exactly where the offence had taken place.
"It is difficult. I also said it last week that it's so difficult nowadays for the referee to decide," Van Gaal said.
"For more than 20, 30 years I've been in this profession, we need video because the referee cannot do it by himself.
"I think [Oliver] is one of the best referees in England but yes, difficult."
Van Gaal felt a video referee could have helped with another key moment in the game when Danny Simpson collided with Jesse Lingard, who was through on goal, but Oliver gave no foul.
"We also have the red card maybe, for Simpson on Lingard," the Dutchman told MUTV.
"I can see why you wouldn't whistle, because it was not a heavy foul, but he grabbed him, so he could have given it."