Brendan Rodgers has already snapped up Bayer Leverkusen midfielder Emre Can, as well as Southampton duo Rickie Lambert and Adam Lallana, but he must add some players to his defence after his side's collapse at the end of last season. With better defending, Liverpool wouldn't have conceded three goals in ten minutes at Crystal Palace, which ultimately cost them the Premier League title.
Left back is certainly a concern given how the injury to Jose Enrique left them short at the position, but it seems that Rodgers is currently concentrating his focus on the centre of his defence, where Martin Skrtel and Mamadou Sakho had some shaky moments during the season, whilst speculation has linked Daniel Agger and Kolo Toure with moves away from Anfield.
That has led to reported interest in Cardiff City defender Caulker, as well as Croatian international Lovren, who both impressed in the Premier League last season. With Rodgers seemingly trying to choose between the two, who should he sign?
Let's start with Caulker. The former Spurs centre back left White Hart Lane in a shock £8m deal last summer, despite being labelled as one of England's brightest young defenders. Still only 22, Caulker was one of the few Cardiff players to come out of their relegation season with praise, having captained the team admirably in the face of bad results. It's no surprise to see clubs lining up for his signature with the Bluebirds now back in the Championship, and whilst QPR and Crystal Palace are both interested, Liverpool are believed to be his team of choice.
Caulker, who has one England cap to his name, worked with Rodgers during their time together at Swansea City, and the Reds boss will know his game inside out. Strong in the air and relatively quick across the ground, Caulker is athletically gifted and has bags of untapped potential at this stage of his career - and we've already seen how young players have flourished under Rodgers at Anfield.
Meanwhile, 25-year-old Lovren was outstanding for Southampton after his £8.5m switch from Lyon last summer. Whereas he may not be quite as quick as Caulker, he has an outstanding reading of the game, is even stronger than Caulker and is a commanding presence in the hart of the defence. Those are qualities which any team needs, and with both having great qualities, it could come down to the fee involved.
Caulker will likely cost around the £8m that Cardiff paid to land him a year ago, whereas Southampton are holding out for £25m for Lovren - almost three times what they paid for him. Lovren may be an instant upgrade in the Liverpool defence, and the kind of calibre of player that the club should be looking at, but they shouldn't be held to ransom in order to get him. Signing Caulker instead would provide familiarity with the manager, as well as a young player with potential who doesn't have expectation on him from the off - and the difference in fee would leave plenty more money for Rodgers to go and spend elsewhere.