There is a race for quality centre-backs in Premier League during the current transfer window, but who are the most in-demand defenders?
Manchester United, Manchester City, Chelsea and Arsenal are just a few of the clubs in need of defensive reinforcements and the hunt is on with a world class centre-back hard to come by.
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So who are the top contenders and where could they be moving to? We take a look below...
It is not the first time Kalidou Koulibaly has been heavily linked with a Premier League move - he is a transfer window regular. This summer, Man City are said to be chasing his signature and, according to multiple media reports, offers have been submitted and Koulibaly is close to an Etihad move.
However, it seems like Napoli president Aurelio De Laurentiis is yet to receive an offer that would force him to part with the defender, recently telling Italian radio station Radio Punto Nuovo: "Without a great offer he does not move."
He played in 25 Serie A games last season - spending some time out with injury - and made 51 tackles, 33 of which were made successfully. He also had an impressive passing accuracy of 91.39 per cent and impressed in the Champions League as Napoli went unbeaten in a group that included then-holders Liverpool.
The Lille centre-back was being looked at as a Koulibaly replacement by Napoli, but Gabriel Magalhaes is set for a move to Arsenal with Sky Sports News reporting a £27m fee has been agreed for the 22-year-old and he is in London for a medical.
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The Gunners have beaten off competition from Premier League rivals Manchester United, who held late discussions with the player's representatives, Everton and Napoli to land one of Europe's most promising centre-backs.
French football expert Jonathan Johnson told the Transfer Talk podcast if Arsenal complete the signing of Gabriel, he could form a long-term defensive partnership with William Saliba, saying: "It would be a pairing of two very good, very promising central defensive talents and potentially a partnership which could serve Arsenal for the best part of the next 10 years.
"He's a very talented guy, physical, he's strong, he's got good technique, he's made for the Premier League. He would be a good addition if Arsenal can pull it off."
Another talented young defender on the list, Dayot Upamecano has been making a name for himself at RB Leipzig and no more recently than in the Champions League quarter-final victory against Atletico Madrid.
He had a tackle and dribble success rate of 100 per cent as well as the joint most touches (99) and joint most clearances (5) with Atletico striker Diego Costa easily kept under wraps.
It is this along with his Bundesliga performances that has seen Arsenal and Manchester United linked with the 21-year-old, although Upamecano signed a new RB Leipzig deal at the end of July to keep him at the club until 2023.
Despite seven major titles with Man City, it has not always been an easy time for John Stones at the Etihad. His performances have come under scrutiny on many occasions and has been guilty of making errors, both at club and international level.
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He spent much of the 2019/20 season in and out of the Man City team and only made one Champions League appearance. Leeds have been linked with the former Everton and Barnlsey defender, while Soccer Saturday pundit Paul Merson recently urged Chelsea to sign Stones.
He said: "Chelsea love to play out the back, they roll it out every time, so you need someone unbelievably good on the ball. If you have pace around them, I think it will help Chelsea; I think Stones would be a great buy, and he has to play in a three.
"Stones has the potential to be great, he really has, but he needs the confidence. At the moment Chelsea have three centre-halves that aren't in the same class as Stones on the ball."
Brighton have already landed the coup of their transfer window with Lewis Dunk signing a new five-year deal despite reported interest from Chelsea.
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Their next task could be keeping hold of 22-year-old centre-back Ben White, who is Leeds' number one transfer target this summer after a successful loan spell at Elland Road last season. He formed an impressive defensive partnership with captain Liam Cooper, featuring in all 46 league games and helping to keep 22 clean sheets as the club won the Championship title.
Leeds have had a third bid for White - worth £25m - rejected by Brighton and it was recently reported by Sky Sports News the south coast club will not sell the defender to the newly-promoted cliub for any price because they want to avoid strengthening a club they consider to be a direct Premier League rival.
Brighton are in talks to offer the centre-back a new deal, but he has reportedly already turned down three contract offers already. His current deal runs until 2022 with the option of a further 12 months and Graham Potter is keen to integrate him into the first team this season.
Chelsea have also been linked with the 22-year-old, fitting into Frank Lampard's approach of mixing young talent with experience, and Tottenham have also been connected in media reports.
Another reported centre-back target for Chelsea, Atletico Madrid defender Jose Gimenez is also being linked with a move to Stamford Bridge and would represent the experience Lampard is looking for. The Uruguay international has also been a reported Man City target in the past.
Gimenez is a two-time Champions League runner-up with Atleti and has won the Europa League during the time at the La Liga club. A series of injuries saw him play in just 21 league matches where he won 16 of the 20 tackles he made, blocking seven shots and making 23 interceptions.
The 25-year-old is contracted to Atleti until 2023 and it would take some big numbers to land their man, but the defender recently spoke of his love for Chelsea and Lampard as a child, saying in an interview with La Liga: "I would have liked to play with Lampard. I always used to watch Chelsea as a kid, loved them."
Chelsea have also been linked with Gimenez's defensive team-mate, goalkeeper Jan Obalk, who said he would consider his Atletico future after the conclusion of the Champions League.
Liverpool, Arsenal and Man City have been linked with recent Europa Legue winner Diego Carlos, who helped Sevilla to a record-extending sixth victory in the competition. It was his acrobatic overhead kick that ultimately won the final against Inter, demonstrating his ability as a goalscorer and a title winner.
But the monitoring clubs may have been put off slightly by Carlos' uncanny ability to give away penalties, doing so early on in both the Europa League semi-final and final. Yes, Sevilla went on to win both games and Carlos saved his own bacon in the final, but he was hugely helped by a "team of giants" as the Brazilian described his team-mates after the victory.
He only joined Sevilla last summer as Julen Lopetegui set about rebuilding the squad and, penalty conceding aside, had a superb debut season in La Liga. He made 35 appearances, scoring two goals - not a bad return for a central defender - and ranked top in the league for clearances completed (174) and headed clearances (105).
Chris Smalling has had something of an Italian renaissance. He flourished during his season-long loan spell at Roma, making 30 Serie A appearances and coming in the top ten for blocked shots (35), interceptions (56) and aerial duels won (95).
Could he be the ready-made replacement Manchester United are looking for? If the names they are being linked with are anything to go by, they will be looking elsewhere for a regular centre-back this summer with Smalling likely to be playing a bit-part or sold elsewhere.
Unsurprisingly, Roma are very keen on bringing the defender back in a permanent deal while Sky Sports News recently reported Newcastle are keen on signing Smalling. Everton and Fulham have all been linked by other media outlets.
Another veteran defender, Jerome Boateng continues to win trophies at the age of 31, recently victorious in Champions League final with Bayern Munich, although was taken off inside 25 minutes after picking up an injury.
German outlet Sport Bild recently reported Bayern would consider an offer for the German if the right one came in while Boateng himself recently admitted he would consider a return to the Premier League.
Manchester United have been linked with him in the past, as have PSG and Juventus, but for now, his future seems very much up in the air.
It was a tough season for Samuel Umtiti and with tumultuous times ahead at Barcelona, he is reportedly on Ronald Koeman's list of players who are no longer required.
The World Cup winner had a season punctuated by injuries and a lack of minutes, playing just 13 La Liga games and three times in the Champions League. His positive test for coronavirus just before the 8-2 defeat to Bayern Munich truly rounded off a horrible year.
Arsenal, West Ham and Everton have all been linked with Umtiti, although he would need to prove his ability to stay fit before joining another club. Manchester United and Chelsea have been linked with the 26-year-old in the past, with a loan deal also a potential option for Barcelona.
However, a report in the Daily Mail at the start of August said Umtiti wants to stay and fight for his place at Barcelona and has no plans to leave. But given his recent injury troubles and a new manager, that decision could be taken out of his hands.
The summer transfer window will run for 10 weeks from July 27 and close at 11pm on October 5.
A domestic-only window for trades between the Premier League and EFL then runs from October 5 and closes on Friday October 16 at 5pm. Follow all the news and analysis on Sky Sports News and across Sky Sports' digital platforms, including with our dedicated Transfer Centre blog.