Ndong who joined the Black Cats from Lorient for a fee of 16m euros.
“We had been pushing to bring in Ndong for quite a while, but we kept getting the message back that he wouldn't be leaving," Moyes told the Evening Chronicle.
“It was only two or three days ago that it opened up and there was a chance that we might be able to sign him.
“We like the look of him, he has good energy, he is young, he will improve with time.
“I think he has a personality to his play.
“I'm not saying he is another N'Golo Kante, but there is a bit of that in his makeup."