The transfer window opens on Jan. 1 and clubs across Europe have a month-long chance to add to their squads before it slams shut again.

But with many clubs preferring to wait until the summer to do their business, which players might move in January? Who could be a bargain because of their contract or playing situation? And who will have to wait six months?

*All transfer valuations estimated

Ready to sign right now

They're in form, are ready to roll and will improve any team immediately. What's the hold up?

MOUSSA DEMBELE
Position: Striker
Team: Lyon
Value: £40m

Dembele was tipped for the top when he was a teenager at Fulham and his subsequent moves to Celtic and then Lyon have not elevated him to where he was expected to be. That could change now as Chelsea seek a replacement for Olivier Giroud, Arsenal (potentially) for Pierre-Emerick Aubameyang or Alexandre Lacazette) and Man United, well, they just need a good young striker.

Teams linked: Chelsea, Man United, Arsenal.

NATHAN AKE
Position: Defender
Team: Bournemouth
Value: £40m

The Dutchman moved to Bournemouth in 2017 having struggled to claim a first-team place at Chelsea, but the Blues put a buyback clause of £40m in his contract and reportedly lead the race for him. The 24-year-old has proven himself in the Premier League and there are plenty of clubs who need a good, young centre-back now.

Teams linked: Chelsea, Man City, Arsenal.

DAYOT UPAMECANO
Position: Defender
Team: RB Leipzig
Value: £68m

One of the most highly-regarded defensive prospects in Europe, the 21-year-old has impressed in the Bundesliga and could be the latest Frenchman to land at Arsenal if the Gunners can stump up his release clause. Top centre-backs will be in demand, so whichever team gets him will have to pay his reported release clause of £68m.

Teams linked: Arsenal, Man City, Tottenham, AC Milan.

TIMO WERNER
Position: Striker
Team: RB Leipzig
Value: £27m

The Germany striker only recently signed a new contract at Leipzig but with a reported £27m release clause included, the big clubs will circle. It's impossible to find a young striker of Werner's quality for that price, so he will have options -- however, many of them will want him to play backup to an already established striker like Tammy Abraham. Roberto Firmino or Robert Lewandowski.

Teams linked: Chelsea, Liverpool, Manchester United, Bayern.

WILFRIED ZAHA
Position: Forward
Team: Crystal Palace
Value: £75m

Having seen a transfer to boyhood club Arsenal fall apart in the summer, and Palace also rejecting a massive offer from Everton, Zaha could push for a move in January. Chelsea have now entered the race for the winger, who has shown himself to be one of the best in the league.

Teams linked: Chelsea, Arsenal, Everton, Dortmund.

Take a gamble?

For whatever reason, these players are struggling at their clubs and may be offloaded on the cheap.

GRANIT XHAKA
Position: Midfielder
Team: Arsenal
Value: £20m

Arteta might also give Xhaka a chance to prove himself after he lost the captaincy for a petulant display towards some jeering fans after being substituted. However, his days at the club also look numbered and Jurgen Klinsmann's Hertha are favourites to land themselves a bargain.

Teams linked: Newcastle, Hertha Berlin, Gladbach, Inter Milan.

MESUT OZIL
Position: Midfielder
Team: Arsenal
Value: £25m

New Arsenal boss Mikel Arteta might be willing to give Ozil a fresh start, but the German's future at the club has been thrown into fresh doubt with his political comments about China. Fenerbahce would love him on loan for the rest of the season but any team coming in for him would have to persuade him to drop his £350,000-a-week wages.

Teams linked: Fenerbahce, LA Galaxy, AC Milan.

EMRE CAN
Position: Midfielder
Team: Juventus
Value: £35m

It's hard to understand why things haven't worked out for Can in Turin, but the German was left out of the club's Champions League squad and has played only a handful of games. At 25, he's still young and his next move will be key. But, as a former Liverpool player, if it's to United then you can expect fireworks.

Teams linked: Man United, Bayern, PSG

GARETH BALE
Position: Forward
Team: Real Madrid
Value: £60m

"Wales. Golf. Real Madrid. In that order." Bale can't be too shocked by the Madrid reaction to his obvious lack of interest in staying at the club. He has won everything at the Bernabeu, but if Real can find a buyer for him then they'll let him go. A lucrative move to China fell through in the summer, but Tottenham boss Mourinho is a big fan of the Welsh winger and could bring him back to north London.

Teams linked: Bayern, Tottenham, PSG, Jiangsu Suning

IVAN RAKITIC
Position: Midfielder
Team: Barcelona
Value: £25m

The summer arrival of Frenkie de Jong has pushed Rakitic down the pecking order and Barcelona are ready to listen to offers for the 31-year-old. A classy midfielder, Rakitic would improve many clubs but he has only a few more years left at the top so could go cheaply. Or he might be included in a swap deal for one of Barca's targets.

Teams linked: Man United, Juventus, Inter Milan, Atletico Madrid.

A bargain to be had?

With their contracts expiring in the summer, clubs can move for these guys now on the cheap or wait to get them for nothing in six months.

CHRISTIAN ERIKSEN
Position: Midfielder
Team: Tottenham
Value: £30m

Eriksen seems to have made it clear that he won't be signing a new contract at Tottenham, but will any club snap him up before the summer? The Denmark midfielder is a quality player and his price (previously £100m) has plummeted. Real are at odds as manager Zinedine Zidane prefers Paul Pogba, but the sharks will be circling.

Teams linked: Real Madrid, Barcelona, Man United, Juventus.

EDINSON CAVANI
Position: Striker
Team: PSG
Value: £10m

It looks as if Cavani has already agreed to a summer move to Atletico, with a three-year deal on the table. Nothing is confirmed yet though, so clubs still have some negotiating time, though the wages he expects are likely to count all but the biggest clubs out.

Teams linked: Atletico Madrid, Inter Miami, LA Galaxy, Chelsea

NEMANJA MATIC
Position: Midfielder
Team: Man United
Value: £20m

The Serbian midfielder has slipped down the pecking order at Old Trafford and looks set to move on. It would be funny if he followed Mourinho to Tottenham, having moved from Chelsea to Man United to be with the manager, but it looks more likely that he'll head abroad. Perhaps a reunion with Antonio Conte in Milan instead?

Teams interested: Atletico Madrid, Tottenham, Inter Milan.

OLIVIER GIROUD
Position: Striker
Team: Chelsea
Value: £5m

Giroud has been frustrated at Chelsea, having been unable to oust Abraham from the starting spot and has barely played. Another to eye a move to Inter, a return to France is also on the cards for the 33-year-old as he seeks more game time.

Teams linked: Inter Milan, Vancouver Whitecaps, Nice, Bordeaux, Marseille, Lyon.

DRIES MERTENS
Position: Forward
Team: Napoli
Value: £10m

With over 100 goals for Napoli in seven years, the 32-year-old looks set for a change of scenery and won't sign a new deal at the club. There are plenty of top clubs being linked with the Belgian though, as his quality is far higher than his price tag.

Teams linked: Arsenal, Bayern, Dortmund, NYCFC, Inter Milan.

Wait until the summer

These guys are going to cost a lot of money and there's some serious negotiating to do. Better hold off for now.

JADON SANCHO
Position: Forward
Team: Dortmund
Value: £120m

Sancho left Man City in 2017 for a measly sum of £8m to get first-team football in Germany and boy, did it pay off. Now one of the most exciting attackers in the game, the 19-year-old can have his pick of clubs and with Erling Haaland arriving at Dortmund, will have a target to aim for unless he's sold in January.

Teams linked: Man United, Man City, Chelsea, Liverpool, Bayern, PSG, Juventus

KALIDOU KOULIBALY
Position: Defender
Team: Napoli
Value: £90m

One of the best centre-backs in the world. it's not hard to see why clubs are circling for Koulibaly's signature. However, Napoli won't let him go without a massive offer that would make him the world's most expensive defender.

Teams linked: Man United, Man City, Chelsea, Liverpool, Real Madrid, PSG.

KAI HAVERTZ
Position: Midfielder
Team: Bayer Leverkusen
Value: £120m

The 'new Ozil' won't move in January, despite all the noise around him, but he won't stay at Leverkusen beyond the summer. At only 20, Havertz has the world at his feet and it's most likely that he'll head to Bayern or Barcelona.

Teams linked: Bayern, Barcelona, Liverpool, Chelsea, Man City, Man United, Real Madrid.

JAMES MADDISON
Position: Midfielder
Team: Leicester
Value: £80m

This season has been a revelation for the former Norwich midfielder and Leicester will want to get as much as Man United paid for Harry Maguire if they sell him. Maddison is clearly well suited to the Premier League, so United or Chelsea would be getting proven quality.

Teams linked: Man United, Chelsea, Tottenham.

DONNY VAN DE BEEK
Position: Midfielder
Team: Ajax
Value: £40m

When Matthijs de Ligt and Frenkie de Jong moved on from Ajax, everyone assumed that Van de Beek would be next. A skilful attacking midfielder, the 22-year-old has plenty of suitors but has already gone on record as saying he won't move until the summer as he doesn't like to change teams midseason.

Teams linked: Borussia Dortmund, Man United, Everton, Barcelona, Real Madrid, Bayern Munich.

MARTIN ODEGAARD
Position: Midfielder
Team: Real Sociedad (on loan from Real Madrid)
Value: £60m

Having joined Real Madrid at age 16, Odegaard has spent years on loan and is only now showing his true potential at Real Sociedad. The Norwegian midfielder told ESPN he wants to stay at the club for another few years before heading back to Real, but the Premier League could be tempting.

Teams linked: Man United, Liverpool, Arsenal, Atletico Madrid.