Liverpool manager Brendan Rodgers says the signing of Dejan Lovren will provide added leadership to a defence that cost the club their first league title is 24 years last season.
Defeat to Chelsea and a 3-3 draw with Crystal Palace ensured the Reds finished two points behind eventual champions Manchester City after conceding 50 goals across the campaign.
The club suffered constant injury problems to their back four with Daniel Agger, Mamadou Sakho and Jose Enrique spending extended periods out injured, but Rodgers hopes the addition of Lovren, in a reported £20m deal from Southampton, will unite the Liverpool defence.
"He's a leader, a very commanding presence at the back and knows his job," Rodgers told Sky Sports.
"He's still got areas in which to improve and to learn. But his overall leadership and he wants to defend first and foremost. Then he wants to lead the line and he can play. I am delighted with that signing because it is very important for us.
"He is an international defender of great esteem and he's still in his mid-20s so he's still got improvements to make. I felt that someone to come in and be a defender on the front foot. He comes up to people and he's brave without the ball.
"The squad was very shallow last season. We felt going into the competitions that we've got that squad depth. We'll get injuries along the way and we want to be competitive in all four competitions we enter but we need a squad."
Lovren, who featured for Croatia at the 2014 World Cup, becomes Liverpool's fifth summer signing after Rickie Lambert, Adam Lallana, Emre Can and Lazar Markovic and will join the club on their pre-season tour of the United States.
Liverpool have meanwhile withdrawn from a deal to bring Loic Remy to Anfield, after the Queens Park Rangers forward reportedly failed a medical.