The Serbia international made the controversial switch from the Premier League champions to their bitter rivals on Monday evening.
Matic was part of Guus Hiddink’s Chelsea team that won the FA Cup at Wembley in 2009 before the midfielder moved to Benfica in 2010.
However, Jose Mourinho re-signed Matic in a £21m deal from the Portuguese champions in the 2014 January transfer window.
The Serb won the Premier League title and the EFL Cup under Mourinho before the Chelsea boss was sacked in December 2015 after a lacklustre start to the defence of their top-flight crown.
Matic still played a key role under Antonio Conte last term as the west London club won the Premier League crown for the second time in three seasons with two games to spare.
However, Tiemoue Bakayoko’s arrival from Ligue 1 giants AS Monaco cast doubt on Matic’s long-term future at Stamford Bridge.
Speaking to Manchester United’s website about his summer transfer, Matic had a message for Chelsea supporters following his big-money move:
“I have enjoyed my time at Chelsea and would like to thank the club and the fans for their support.”
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