While most football clubs will be busy strengthening their sides this transfer window, many will be looking holding their own January sales.
Of the Premier League title challengers, that sentiment perhaps applies most to Chelsea, with several world-class talents struggling for game-time at Stamford Bridge this season.
Indeed, the rumour mill has gone into overdrive regarding departures from west London in the last few months. But who will actually leave Chelsea this January?
Juan Mata's situation at Stamford Bridge has entered precarious territory in recent weeks. The Spaniard has not completed 90 minutes since the Blues' 3-2 defeat to Stoke and did not play a single second of their most recent 2-1 win over Liverpool.
This could be considered a normal part in the rotation of a large squad but, with the January window now open, Jose Mourinho does not seem to be issuing any particular hands off warnings.
If Chelsea want to strengthen this January, they have made it clear that they would need to comply with Uefa's Financial Fair Play regulations. The funds from a Mata sale - both in terms of transfer fee and wages - would be a big help towards this.
The Spaniard has thus far disappointed Mourinho since the Special One's return to west London, with a failure to track back while playing in an attacking midfield position being the Portuguese coach's main concern. And with Eden Hazard, Oscar, Andre Schurrle and even Willian faring better in comparison, there is nothing stopping Chelsea from cashing in on Mata this winter.
Several European clubs, including Paris Saint-Germain, have showed concrete interest in signing the Spaniard to date.
Kevin De Bruyne?
Another midfielder struggling for game-time this season is Kevin De Bruyne.
The Belgian has made just three Premier League appearances this term and has attracted interest from the Bundesliga and Atletico Madrid.
A January departure, then, seems almost imminent, although the move is most likely to come in the form a loan deal.
De Bruyne, of course, spent his first season as a Chelsea player out on loan at Werder Bremen - and a lack of first-team football this time around means another temporary move away looks the ideal solution.
A slightly more controversial subject, Ashley Cole's future at Stamford Bridge has been questioned in recent weeks. There has been no concrete talk of any bids for the left-back but his fall behind Cesar Azpiliceuta in the pecking order has sparked speculation about a Chelsea exit.
The 33-year-old's appearance at Arsenal's Christmas party prompted further discussion, with two clubs reportedly happy to offer the England defender a place at left-back being the Gunners and Liverpool.
It seems unlikely that Mourinho would let one of his favoured players leave west London but, with Chelsea's transfer policy increasingly focusing on younger squad members, Cole's days could be numbered at the Bridge, whether he leaves in January or this summer.
Perhaps the most likely departure this winter, however, is that of Michael Essien. Like De Bruyne, the 31-year-old has made just three league appearances this season, while he was been criticised for his poor form - especially after a costly error against Southampton.
Unlike De Bruyne, though, Essien does not have age on his side and could be subject to the same scrutiny as Cole in the coming weeks.
Chelsea have been short in holding midfield at key points this season but Mourinho has seemed reluctant to use a player he has formed a tight bond with over the years. As such, the Blues look likely to say goodbye to one of their most faithful servants this January.
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