Liverpool is set for a busy summer once the transfer window opens with new American owners Tom Werner and John Henry keen to flex their financial muscle and improve the Reds' squad.

Despite the dramatic improvement on the pitch since Kenny Dalglish —now signed in as the permanent manager—took over in January, there are still obvious deficiencies which need addressing in the same manner that Damien Comolli, Ian Ayre and Dalglish applied to the striker's vacancy when Fernando Torres departed for Chelsea.  They repaired these vacancies with a quality replacement or two.

The success of Luis Suarez and, to a lesser extent because of injury, Andy Carroll, has given Liverpool supporters hope that this summer will be a big one for the Reds as they bid to return to the top of domestic football.

One of the key areas of any team is the centre of its defence and though Liverpool have four senior members of the squad at present—Jamie Carragher, Daniel Agger, Martin Skrtel and Soto Kyrgiakos—it is expected that at least one and possibly two of them could be moved on in the summer, making way for a new addition.

Here we examine the Top 6 centre backs from around Europe who have been linked with a move to the Reds recently.

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Phil Jones (Blackburn Rovers)

Rovers' beast-sized teenager Phil Jones has made a huge impression on Premiership managers and scouts this season as his robust style of play and impressive versatility, often performing at left back or in the centre of midfield, have made him an important part of Steve Kean's side.

Strong and aerially good, Jones would certainly be likely to cost in the double figures of millions but at just 19 years of age, could potentially marshal a defence for the next dozen years.

Still has plenty to learn of course, but the talent and mentality is certainly there.

Gary Cahill (Bolton Wanderers)

Reported as almost a 'done-deal' in certain circles, Bolton's aggressive Englishman Gary Cahill has impressed over the past two seasons after joining from Aston Villa and was capped this season by England.

Sturdy and comfortable on the ball, Cahill also possesses a fair amount of pace and has a good eye for goal at set pieces.

Likely to cost anywhere from £12 million to £15 million whenever he leaves the Reebok Stadium.

Mateo Musacchio (Villarreal)

Argentinian youngster Mateo Musacchio is another who has impressed this season, this time playing in the top flight in Spain for Villarreal.

He is composed on the ball and strong in the tackle and was reportedly watched by Damien Comolli's team earlier in the season.

Though not a regular in the national side, Mateo has an Italian passport, meaning he would not need to go through the rigorous process of applying for a work permit. 

Jan Vertonghen (Ajax)

According to Dutch media, Liverpool is set to return to the scene of their January adventures to bid for Luis Suarez's ex-team mate Jan Vertonghen.

The Belgian centre back is classy and comfortable on the ball and is another player equally at home in a deep midfield role.

Partnering Toby Alderweireld—another player who would be a welcome target—in the centre of Ajax's defence, he is a reassuring presence and a good organiser.

Dejan Lovren (Olympique Lyon)

Dejan Lovren is a Croatian centre back who plays for Lyon in France. Just 22 years of age this summer, he has remarkable top flight experience for a young centre back.

Renowned as being good in the air and in one-on-one situations, Lovren is usually a first choice for the French outfit and is a surprise link to the club; quite possibly merely born of Comolli's French connections.

Still, you never know.

Ryan Shawcross (Stoke City)

A Manchester United youth player, Shawcross is set to lead out his side as captain of Stoke at Wembley tomorrow in the FA Cup Final against Manchester City.

Several media outlets have linked him as the no-nonsense, tough tackling centre back that Dalglish will turn to in the summer, with prices ranging from £10 - £14 million.

Shawcross is a good reader of the game and is generally strong in the air.