Yorke is demanding the players prove they're playing for manager David Moyes.
He told the Daily Star Sunday: "I'd like to think they're all playing for him but results haven't shown that, clearly.
"When that happens there will always be question marks over the layers not wanting to play for a manager. But it's the obligation of the players to understand they're representing Manchester United football club - and our brand throughout the world.
"The players are paid to play for the manager - whoever is in charge - and it's up to them to make sure that happens.
"Certainly, they now have some great games to do that."
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