Chelsea have moved into pole position in the race for Southampton centre-half Virgil Van Dijk, with the Saints considering Liverpool's Mamadou Sakho as a replacement. Van Dijk will be one of the most sought after players this summer with his club anticipating bids in excess of £50 million – which would eclipse any previous Premier League fee for a central defender. Southampton will certainly want more than the £47.5m Manchester City paid Everton for John Stones last season. City are the most realistic rivals to the current league leaders for Van Dijk's signature. He will have his pick of Premier League clubs but at this stage Chelsea are leading the chase for the Dutchman. Chelsea are currently thriving under Antonio Conte with his preferred system of three centre-halves, a formation that would suit Van Dijk given his ability to play out of defence. With John Terry unlikely to be offered a new contract at Stamford Bridge, a top quality replacement is a priority. Van Dijk has been absent since January with a foot injury and is struggling to play again this season. It could be he has played his game for the club as Southampton are already planning to fill the void when the 25-year-old departs. Chelsea's Nathan Ake could head in the opposite direction. He is valued at £15 million. Liverpool's Sakho – currently on loan at Crystal Palace – is another possible replacement. Southampton held discussions with Liverpool about a move for the 27-year-old in January but baulked at the £20 million price tag. Since then the Frenchman has made an immediate impression at Selhurst Park, assisting Palace's relegation fight with some imperious performances. But there was no purchase clause included in the loan arrangement, so if Palace want to sign the player permanently they will have to join a summer auction or hope Sakho has fallen in love with their club to the point where he is determined to stay. Several clubs appear to have been waiting to see how Sakho performed following his lengthy lay-off, while the player also wanted a deal enabling him reassess his options in the summer as he continues to rebuild his reputation after a troubled end to his Anfield career. Napoli are another club to have registered an interest with Liverpool for Sakho. Like Southampton, they are expecting to lose their highly rated centre-back Kalidou Koulibaly at the end of the season. Numerous Premier League clubs, including Chelsea, are keen on Koulibaly. Chelsea tried to sign him last summer but walked away when he was valued at £50 million by his Italian club. Liverpool will also be seeking an additional centre-half this summer, but their chances of making Sakho a lightweight in deals for Van Dijk or Koulibaly are slim given the competition for their services and the huge fees. It promises to be a summer where all the leading clubs are frantically searching for defensive reinforcements and several centre-halves could be on the move, with Burnley's Michael Keane's performances for England reinforcing the view he will soon be making a big money transfer. Everton are among those interested in Keane. A deal was not possible in January and Keane's value continues to soar. Given the ease with which Keane stepped onto the international stage last week the competition for his signature will also intensify. Meanwhile, Liverpool hope their captain Jordan Henderson will make his return to the squad for this weekend's Merseyside derby. Henderson has been missing for the last month with a foot injury, but will step up his training schedule this week. Jurgen Klopp will also be sweating on the condition of Brazilian duo Philippe Coutinho and Roberto Firmino as they remain on international duty until midweek. Liverpool will organise a private jet to ensure a swift return for the players from South America following Brazil's World Cup qualifier with Paraguay, a fixture kicking off in the early hours of Wednesday morning English-time. Klopp wants the pair back on Merseyside at the first opportunity as he continues to prepare for Saturday's early-kick against his neighbours but Coutinho and Firmino must return from Sao Paulo and it will cost in the region of £120,000 to secure their personal transport. During previous international breaks the costs have been shared with other England-based Brazilian internationals, such as Manchester City. Ideally, Klopp wants Coutinho and Firmino training with their team mates on Thursday morning.
