He told liverpoolfc.tv: "We are really pleased to have signed Martin. We had our scouts watching him for two months and a centre back was a necessity for us. We are really lucky because we have Daniel Agger coming back and now Martin Skrtel, so the competition in this position will be good for me and good for the team.
"He is more like Carra than Agger. He is a player who is strong and physical, he is good in the air and quick. I think he will settle here quickly."
The Slovakia international is the most expensive defender in Liverpool history and Benitez added: "For me the price is not the key. When you talk about the market now the prices for players are crazy. We were checking centre backs.
"One who was 18-years-old, the other was 21 years old and another one 23/24. The price was 14 million euros for one, 16 million euros for another one and the third one was 20 million euros, so the market is crazy. We have signed a good player at the right price. Martin is 23 and he is a player for the present and the future. We are building a better squad than we've had before and also one with a lot of young players than can be the spine of the team in the future."