"I know him quite well after being together at Vitesse for a couple of seasons," Buttner told the Western Mail.
"I knew he was strong in the air and it was a good finish to win the game against us.
"I was with him every day training and you could see that he was too strong in Holland. It was too easy for him. He deserved to go to a better club.
"£12 million is a lot of money for any player but he just needs time. It was the same with me. When you are new, you are away from family and friends and football in this country is different from Holland.
"You need time to learn about English football, and that goes for me and Bony as well.
"Everything is quicker and the players are stronger.
"They are two important things, everything goes quicker with the ball and the players are better than in Holland.
"But you can see he's scoring now and he deserves that because he's a good player.
"He's a good professional and will train a lot after training has finished. I hope he will be successful."
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