The defending Premier League champions made the surprise decision to offload the Serbia international in August 2017.
Matic was a key member of Antonio Conte’s team alongside N’Golo Kante as Chelsea FC won the Premier League title in 2016-17.
The Blues signed France international Tiemoue Bakayoko in a £40m deal from Ligue 1 giants AS Monaco.
A month later, Matic departed to strengthen one of Chelsea FC’s fiercest Premier League rivals ahead of the 2017-18 campaign.
The Blues have struggled to maintain their high performance levels in the current season without Matic to protect their defence.
Bakayoko has struggled to adapt to the Premier League, while his fellow summer signing Alvaro Morata has also been underwhelming.
Former Manchester United defender Neville believes Chelsea FC made a big mistake selling Matic to the Red Devils.
“They did try to go for Lukaku,” Neville told Sky Sports.
“They didn’t call on the situation with Costa. Matic is a strange one.
“It was suggested Bakayoko was a far better talent but Matic brings an authority and a control to the pitch.
“Letting him go to Manchester United, who are going to potentially finish second, was a mistake.”
Matic won two Premier League titles in three seasons at Chelsea FC, while the Serbian lifted the League Cup in 2015.
Chelsea FC are in fifth place in the Premier League table and eight points adrift of fourth-placed Tottenham Hotspur.
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