"He is a tough defender who is strong and good in the air. He has a strong character and we were looking for these things," said Benitez.
"He can score goals and will be a threat from corners and free-kicks. He's very strong in defence but he will need time as always to settle into the Premier League. He will be a very good signing for us.
"We knew the player when he was with Rangers and we've been watching videos of him at Frankfurt and the national team. Our scout department had a lot of information.
"We've talked about the things he's done before and the things he'll have to do for us. It was good. He knows what we want and he's ready to work."