Here are 20 defenders who have been linked with January transfer window moves.
In the last January transfer window, there were notable defenders who transferred such as Christopher Samba (Anzhi Makhachkala to Queens Park Rangers), Mapou Yanga-Mbiwa (Montpellier to Newcastle United), Mathieu Debuchy (Lille to Newcastle United), Nacho Monreal (Malaga to Arsenal) et al.
If there is a defender you feel should be on this list, please comment below.
Manchester United have abandoned the chase for Sevilla left-back Alberto Moreno, as per Estadio Deportivo (h/t Football Espana).
Extending Moreno's contract by four years last October ensures Sevilla are in the power position should a suitor be interested in the left-back.
UEFA.com reported the deal:
Sevilla FC have rewarded full-back Alberto Moreno with a four-year contract extension on the day the 21-year-old received his first senior international call-up by Spain.
[The] new Sevilla deal...runs until June 2018 and contains a €30 [£24.9] million buy-out clause.
Sevilla have a noted history in selling defenders to major European teams: Adriano (Barcelona), Dani Alves (Barcelona), Martin Caceres (Juventus), Sebastien Squillaci (Arsenal) and Sergio Ramos (Real Madrid).
Manchester United management see Porto left-back Alex Sandro as a potential successor to Patrice Evra, as per David Wright at the Express.
What Sandro will bring is width because he can run all day.
In the 1-1 draw against Austria Vienna, their right-back Fabian Koch was worked overtime by Sandro's lung-bursting runs.
Manchester United manager David Moyes is willing to allow left-back Alexander Buttner to leave for Galatasaray, as per Simon Jones at the Daily Mail.
When Buttner was subbed on against West Ham United, he was all over the place.
His positioning was terrible and he temporarily forgot how to play the offside trap, which sums up his career with United.
Andrea Ranocchia could be on his way out of Inter Milan, as per Ben Jefferson at the Express.
Ranocchia has been a defensive liability as was evident in a 3-3 draw against Parma and a 4-2 defeat to Napoli.
He picks up so many pointless yellow cards and would be a big risk if major clubs sign him.
Barcelona continue to monitor the development of Athletic Bilbao's Aymeric Laporte, as per Tre' Atkinson at Inside Spanish Football.
Laporte is an aggressive proactive defender with world-class potential.
He dominated Cesc Fabregas whenever the Barcelona false nine got close to Bilbao's penalty box during the Basque club's 1-0 win over the Catalan club.
Laporte recently extended his contract, so Bilbao won't be in any rush to sell him.
Chelsea will only consider selling David Luiz if a £35 million plus bid is lodged, as per John Drayton at the Daily Mail.
"Chelsea defender David Luiz is attracting fresh enquiries from Bayern Munich and Barcelona," Drayton wrote. "But Jose Mourinho is set to keep the Brazilian unless either club bids £35 million."
Luiz is not good enough to be a weekly starter at Bayern and if Barca want to continue having technically superb but defensively suspect centre-backs, then Luiz is their man.
Southampton are set to bid £12.5 million for Cagliari defender Davide Astori, as per Tuttosport (h/t the Independent).
Astori is the Italian version of Titus Bramble—once a promising player but has since declined drastically.
He makes too many mistakes to be even worth £1 million let alone £12.5 million.
Manchester United are targeting Porto's Eliaquim Mangala, as per Alan Nixon at the Mirror.
"His physique and talent make him ideal for the Premier League," Nixon wrote. "But it will still take a massive cheque to get Mangala to the red half of Manchester next month."
United need a dominant world-class midfielder, so signing Mangala is not going to change their fortunes.
If Real Madrid left-back Fabio Coentrao is not guaranteed regular playing time, he will push for a move away, as per AS (h/t/ Inside Spanish Football).
Should Marcelo suffer an injury, who will replace him?
Nacho? Well, he is a centre-back and he would be found wanting against elite right-sided attacking players.
There is no reason for Real to let Coentrao, who hasn't even fully recovered from his injury, to leave since it would be disastrous if Marcelo is out for an extended period.
Everton defender John Heitinga has rebuffed an approach from West Ham United.
"You must be convinced that you are making a right step and that [thought] was with me, so I cancelled West Ham," Heitinga said, as per Andy Hunter at the Guardian. "There is some, so I'm confident that I can find another club before January 31."
Sylvain Distin, Phil Jagielka, Antolin Alcaraz and an interesting prospect in John Stones are all ahead of Heitinga at Everton.
Heitinga should join a mid-tier Serie A club that is willing to give him regular playing time.
Aston Villa, Everton, Monaco, Newcastle United and Tottenham Hotspur have been linked with Manchester City centre-back Joleon Lescott, as per the Manchester Evening News.
Manchester City manager Manuel Pellegrini has no intentions of letting Lescott leave.
"Joleon Lescott is a very important player for us," Pellegrini said, as per Eurosport. "We will see what happens in the future but for the moment he is still here and he is a very useful player for our team."
Saint Etienne centre-back Kurt Zouma is a transfer target for Arsenal, Chelsea, Manchester City and Monaco, as per Dominic Fifield at the Guardian.
"Chelsea are considering making a formal bid of about £13 million," Fifield wrote. "[Zouma is] in the middle of a 10-match domestic ban after his tackle on Thomas Guerbert during a goalless draw with Sochaux last month left his opponent with a broken leg."
Zouma is a reactive centre-back, often relying on strong positioning rather than brutish tackling.
He has only picked up four yellow cards in his last two seasons, so it was out of character for him to go in so hard on Guerbert.
Everton manager Roberto Martinez will attempt to hold on to left-back Leighton Baines as long as possible but it is inevitable he will leave.
"I have said it many times that in football you can't fight the trend of the game," Martinez said, as per John Nisbet at the Independent.
"But what you can dictate is the timing and everything you do should be for the good of the club."
Baines is 29 years old and if Everton were to receive a £20 million bid, they should accept it as they have a replacement in Bryan Oviedo.
Southampton left-back Luke Shaw will continue to resist a big-money move, as per Jeremy Wilson at the Telegraph.
"[Shaw] believes that his development is best served by staying where he is," Wilson wrote. "There is confidence at Southampton, however, that Shaw will remain their player not only after this window but also next season."
Shaw is costing himself millions of pounds in the short-term but, by looking at the bigger picture, he is safeguarding his long-term future by playing regularly at Southampton.
Other rising England youngsters should opt for what Shaw is doing rather than taking the money now at a big club, then wondering why they're playing in League One a few seasons later.
Napoli and Roma are two of many clubs looking to sign Juventus defender Martin Caceres, according to his agent Daniel Fonseca.
"Roma, Napoli and other big clubs asked about Caceres," Fonseca said, as per Tuttosport (h/t Football Italia). "However, Martin is in love with Juventus and wants to remain in Turin."
When Caceres started at right-back in the 2-2 draw against Real Madrid, he struggled defensively, being culpable for Cristiano Ronaldo's goal.
Caceres has the physical tangibles which is why he has been on the books of Barcelona and Juventus, but he hasn't kicked on to become a world-class footballer.
Injuries have been a barrier, though he seems to switch off during games, hence why he is just a backup.
The latest statement by Josep Maria Orobitg, the agent of Barcelona defender Martin Montoya, suggests there is a chance the Spaniard will leave Barca.
"If we cannot reach an agreement on a new contract, Montoya will be free to find a new club," Orobitg said, as per TMW (h/t talkSPORT). "There have been no recent contacts with the leaders of Barcelona."
Surely he understands he is the heir apparent to Dani Alves.
Montoya started 11 La Liga games for Barca last season and already has seven this season.
It makes no sense for him to leave Barca unless he is going to a mid-tier club for week in, week out regular football.
Last November, Spanish football writer Guillem Balague revealed that Barca have no intentions of selling Montoya, as per Bleacher Report: "Barcelona do not want to sell Montoya, least of all in January. The team are struggling with injuries, and they view him as the successor to Alves."
Villarreal will only let centre-back Mateo Musacchio go for £41.4 million, his buyout clause.
"Musacchio has a contract until 2018, therefore he will be here for four more years," Villarreal club president Fernando Roig said, as per Francisco Acedo at Sky Sports. "If he is wanted, then for Villarreal it is fine, but only if the money is paid up front."
Musacchio reads the play excellently and cuts off passes well, accumulating 54 interceptions this season.
Freiburg's Matthias Ginter has confirmed Bayern Munich and Borussia Dortmund want to sign him but said a January transfer was out of the question, as per Bild (h/t Bleacher Report).
If Ginter joins Bayern, he could be another Jan Kirchhoff, where he wastes half a season before being loaned out.
Should Freiburg suffer relegation, he should look to make an intermediate step up, rather than joining Bayern or Dortmund which may adversely affect his playing time.
Stoke City are looking at bringing in Michael Mancienne from Hamburg on loan, as per Alan Nixon at the Mirror.
"Stoke boss Mark Hughes wants to bring Michael Mancienne back to the Premier League," Nixon wrote. "Former Chelsea defender Mancienne is prepared to return to England."
Mancienne has had a rough time at Hamburg and is an afterthought in Bert van Marwijk's regime.
Ryan Bertrand is a transfer target for Everton and Liverpool, as per Sachin Nakrani at the Guardian.
"The 24-year-old appears to have been identified by Brendan Rodgers as the man to solve his ongoing left-back problems," Nakrani wrote. "But he could face competition from Merseyside rivals Everton."
If Liverpool want another handy but not elite Chelsea player in Bertrand (having signed Victor Moses on loan), they can have him.
Everton don't need Bertrand since it is clear Bryan Oviedo is Leighton Baines' long-term successor.