Title chances and hopes of beating the drop could hinge on what business clubs do in the window with so much riding on their Premier League futures ahead of next season’s mammoth TV deal.
Here are seven players who will attract interest in January and could help define a team’s season.
The Premier League’s 15-goal joint top scorer has been linked to the big boys after his stunning season — and it is not hard to see why.
Vardy scored in 11 straight games to set a new Premier League record, helping transform the Foxes into shock title contenders.
They sat top of the table on Christmas day, 12 months after being bottom over the festive period last year. The Foxes will not want to sell and with England striker Vardy having signed a four-year deal last year they are in a strong position to keep him.
Along with Vardy, the Algeria winger is one of the stars of the season.
The Foxes plucked the 24-year-old from Le Havre for around £400,000 (€544,000) in 2013 and he has proved to be a brilliant bargain, helping them to promotion, survival last season and now to the top of the league.
He dismantled Chelsea earlier this month to underline what a stellar season he is having — and has been linked with Arsenal.
Mahrez has scored 13 goals from the flanks and Leicester will fight to keep a player who signed a new four-year deal in August.
The Watford striker has taken the top flight by storm this season and has plundered 14 goals for the Hornets.
His partnership with Troy Deeney, who has netted six times, has powered Quique Sanchez Flores’ side away from any relegation trouble.
They look set to stay in the Premier League after last season’s promotion and Nigeria international Ighalo is key.
His power and pace has seen him net against Liverpool, Chelsea and Everton and he will have his admirers.
The Belgium international has been restricted this season due to the fabulous form of Gerard Deulofeu.
Boss Roberto Martinez insists the midfielder remains in his plans at Goodison Park but with Euro 2016 just six months away he could face a struggle to convince the 28-year-old to stay.
Mirallas said in November he would consider leaving the Toffees if he failed to get regular first-team football and he has only started one game since.
There will be interest with Monaco linked to the former Olympiacos man, who has spent the last three-and-a-half years with Everton.
While Southampton have failed to hit the heights of previous seasons Senegal international Mane continues to impress.
He was heavily-linked with Manchester United in the summer and Louis Van Gaal’s side have again been credited with an interest for January.
Mane has scored seven goals in 24 games for the Saints this term having netted 12 times last season after moving from Red Bull Salzburg.
Adam Lallana, Luke Shaw, Morgan Schneiderlin and Dejan Lovren have all left St Mary’s in the last 18 months and Mane could be next.
With the Premier League’s new TV deal kicking in next season the desperation to stay in the top flight will grow.
January is the last chance for clubs to roll the dice to ensure top flight survival and Austin would be a fine option having scored 18 goals last season, despite QPR’s relegation. Out of contract at Loftus Road at the end of the season, Rangers would not be able to demand the £15m (€20.4m) they wanted for Austin in the summer.
A cut-price deal could be an option in January with Crystal Palace, despite not being in danger of the drop, in need of a new striker especially with Patrick Bamford heading back to Chelsea.
Despite being promised more first-team football by Jose Mourinho the 19-year-old has started just three games for Chelsea this season.
Mourinho’s exit could see the England U21 international given more chances at Stamford Bridge but, if not, there will be a queue for his services.
Half the Premier League would be able to offer the talented youngster playing time and he would be an asset for any club aiming to stay clear of the drop.
While Loftus-Cheek may not be able to hold down a regular spot at Chelsea, experience away from the Bridge would be invaluable.