Berba hit the winner against Stoke City on Saturday.
Ruiz said: "Whatever it looks like, he does care. He is a different person, he doesn't talk to everyone, but when you go up to talk to him, he is open.
"You see sometimes by his body language that he really wants to win. That means he cares. He is one of the best players I've played with. I don't remember one player with the same skills as him.
"We try to look for him as we know he keeps the ball and he can score, like he did in this game. It is easy playing with him as you can give him the ball and he will not lose it, and you can also get it back from him.
"Also, with his movement, he is very smart to play in front of and that makes for a good team player."