The January transfer window is mostly a bad idea.
Over the summer, there are no standings, and everyone has time to find new players. In January, very real stakes have been established. Some teams are fighting relegation, while others have slipped into a chase for a Champions League spot, and a select few get to take part in a title race.
So not only is the downside to losing one of your best players clear -- get relegated, miss the Champions League, lose the title -- but since the window is so short and almost everyone else feels some version of this pressure, too, it's even harder to find a replacement. On top of that, any team that really wants to sign a new player in January is, by definition, desperate. They want to avoid relegation, finish in the Champions League spots, or win the league.
Nobody wants to sell (supply!), and the teams that want to buy really want to buy (demand!), so January transfers tend to cost about 20% more than the same moves would over the summer. In a strange way, the teams best-positioned in January are the ones who aren't at risk of relegation but also can't realistically win anything, either. In other words, the teams that can afford to sell.
But, well, no one wants to read about which teams should sell this January -- almost everyone wants to read about what new player could join their favorite team. So, ahead of the window opening, let's run through all 20 Premier League teams, see what their biggest needs are, then try to connect them with a team that's in a position to let one of their best players leave and pick the player they should sign.