What do you buy for the man who has everything? Some 14 points clear at the summit of the Premier League table and with perhaps the most complete squad in the division's history at his disposal, Pep Guardiola has been given the green light to strengthen a Manchester City side that is already operating at the peak of its powers.
Even with the loss of £50m signing Benjamin Mendy to a serious knee injury and John Stones' recent absence after a hamstring problem, City's irresistible form has not wavered – with a goalless draw against Crystal Palace their only blemish since August.
But with Champions League dreams still waiting to be realised, there is little point in them standing still if the opportunities to strengthen further are there. Even with teams desperate to cling onto their players during the mid-season window, the Manchester club have pockets deep enough to convince most to do business. Whoever Pep wants, Pep could very well get.
What they need
'Need' might not be the right word, but City may benefit from another centre-half among their ranks. While Stones is expected to return in the coming weeks, Vincent Kompany's occasional injury comebacks – the latest of which saw him last just 11 minutes against Newcastle United – leaves room for another option. Questions remain over Eliaquim Mangala and while Fernandinho provides a capable presence when occasionally dropping back, a more natural option would surely be preferred.
Who could join
City may have missed the boat on Virgil van Dijk, with West Bromwich Albion's Jonny Evans a possible alternative. After City failed in their pursuit of the former Manchester United defender in the summer, the Baggies are now prepared to let him go mid-season. Burnley's James Tarkowski and Real Sociedad's Inigo Martinez are also options.
The loss of Mendy initially left Guardiola pondering a new left-back, but Fabian Delph's impressive form filling in for the Frenchman on the left may have changed those plans. But with the return of the Champions League and FA Cup commitments, another body could be brought in, with Benfica's Alex Grimaldo formerly linked with a move to the Etihad Stadium.
Of course, the latest instalment of the Alexis Sanchez saga is expected to dominate the month. After his deadline day move from Arsenal fell through in the summer, City will reportedly try to bring the Chile international in this month to bolster an already frightening forward line in a move that could cost in the excess of £50m.
Who could leave
Guardiola shipped out all the noticeable dead wood in the summer and in all honestly, there isn't much left of it lying around. Mangala may fall further down the pecking order should another centre-half arrive in January, but after his display against Manchester United, he may be held onto until the end of the season.
What the manager has said
"In the winter window and summer break we are going to ask everyone if they are happy or not, if they are comfortable being in the position they are - playing or not playing. They have to decide because the future will be like this.
"We always want players that want to stay here."