They are the most successful teams in Premier League history, securing 18 titles between them since the inception of the top flight in 1992. Despite their rivalry on the pitch, the two have done a surprising amount of business off the field.
Joining Chelsea initially in 2009, Matic struggled to make an impact for the Blues, making just three appearances before leaving to move for Benfica.
However the return of Jose Mourinho to Stamford Bridge in 2013 saw Matic also make his return to the Premier League in the following January. He was an integral part of Chelsea’s title wins in 2015 and 2017, before Mourinho came calling once again.
He made the the £40m move to Old Trafford in the summer of 2017, where he has become one of the first choice central midfielders alongside Paul Pogba.
Juan Sebastian Veron
There was a great deal of excitement when Juan Sebastian Veron moved to the Premier League back in 2001. He joined Manchester United for an English record transfer fee of £24.3m after an impressive spell in Italy.
Despite his obvious qualities, the Argentine had difficulty adapting to life in the Premier League, and despite a foul mouthed tirade by Sir Alex Ferguson who said he ‘is a f*cking great player’ and ‘you’re all f*cking idiots’, he eventually made a £15m move to Chelsea in 2003.
He had a good start to his career at the Bridge, but ultimately only made 15 appearances for the Blues before being allowed to join Jose Mourinho’s Inter Milan in 2004.
Coming through the ranks at Manchester United, Hughes had a two year spell at FC Barcelona (including a year on loan at Bayern Munich), before returning to Old Trafford in 1988 for a club record £1.8m. He spent a further seven years with the Red Devils, scoring 163 goals in 473 appearances, winning two Premier League titles, three FA Cups, one League Cup, one Cup Winners Cup and one Super cup.
He finally ended his Manchester United career in 1995, moving to Chelsea for just £1m. During his time with the Blues, he added another FA Cup, League Cup and Cup Winners Cup medal to his collection.
Joining Chelsea in 2011 for £10 million from Anderlecht, Romelu Lukaku was considered as ‘the next Didier Drogba’. However, as is often the case at Chelsea, the Belgian wasn’t afforded many chances to make an impression and was sent out on loan to West Brom and Everton.
He ultimately made that move to Goodison Park a permanent one, where he would score 68 goals in 141 Premier League appearances for the Baggies and the Toffees combined. This excellent form in front of goal prompted a transfer scramble in 2017, with both Chelsea and Manchester United heavily linked with the player, with Chelsea thought to have been the favourites for his signature.
However it was Manchester United (and that man Jose Mourinho again) who got his man, with United agreeing to pay Everton £75m for his services. He has had an excellent start to life at Old Trafford, dislodging Zlatan Ibrahimovic as the first choice striker, scoring 27 goals in 51 appearances for the Reds in his first season at Old Trafford.
And finally, Juan Mata! Moving to Chelsea from Valencia in 2011 for £23.5m, the Spaniard would win the double in his first season with the Blues, lifting both the FA Cup and Champions League trophies.
The following year, he followed that up with victory in the Europa League, winning the clubs Player of the Year award in each of his first two seasons at the club, having scored 32 goals in 118 appearances.
The start of his third season became more difficult for Mata under the returning Jose Mourinho, who ultimately sanctioned his £37.5m move to David Moyes’ Manchester United in January 2014, much to the dismay of Chelsea fans. Since his arrival at Old Trafford he has become a fan favourite, scoring 41 goals in 193 appearances.
The arrival of that man Mourinho at United in 2016 suggested that Mata could be allowed to leave, but the Spaniard continues to be one of the first names on the teamsheet.