Benitez said: "We've had a problem with centre-backs as we couldn't sign Heinze and later Agger was injured.

"That's forced us to play with Sami Hyypia, who is 34, and Jamie Carragher in all the matches, twice a week - and it's not easy for them to cope.

"Our idea is to bring in a centre-back and to balance the team in this position."