Manchester United boss Erik ten Hag says the squad's Portuguese speakers are helping Casemiro settle.
The Brazil midfielder has admitted he needs to learn English.
Ten Hag said, "You can see immediately the impact that he can have so we are really pleased that he is here.
"He's talking Portuguese and the players who speak it will help him and he has already said he wants to learn English very quickly and that's the way he is. He wants to learn, he wants to adapt and he wants to perform.
"And I'm sure he'll do that really quickly so he can contribute to our success."