The league leader is looking to get even stronger in the new year.
Arsenal hosts Mauricio Pochettino's team at the Emirates Stadium.
He is believed to have played a crucial role in Romelu Lukaku's move to Old Trafford.
Many regard it as the most exciting league in world football.
The Portuguese star is said to be "angry" at the Santiago Bernabeu.
The Frenchman has been manager at the club since 1996.
The window reopens for a month at the beginning of the new year.
The German playmaker's contract expires at the end of the season.
The Portuguese coach's agent has reportedly been speaking to another club.
The club has a few players with contracts expiring at the end of the season.
Chelsea beat Manchester United 1-0 on Sunday but the Brazilian watched from the stands.
Jose Mourinho returned to the stadium where he won three Premier League titles.
Arsene Wenger has wanted the French midfielder since last season.
The Manchester United manager is already considering the signings he wants to make in January.
Zinedine Zidane's Real Madrid travel to London on Wednesday for the Champions League clash at Wembley.
Arsenal travels to the Etihad Stadium, where Alexis Sanchez may wish he'd moved to.
Manchester United may have had a good start to the season, but life isn't all sunshine and rainbows at Old Trafford.
The French midfielder has been sidelined for six weeks with a hamstring injury.
Both Premier League clubs are planning to bolster their squads in January.
Many names have been mentioned for the hot seat at Goodison Park, so who can save Everton?
The Frenchman only signed a new contract at the club five months ago.