The Red Devils have been linked with a move to sign the Brazil international from the west London side this summer.
The Blues sold Serbia international Nemanja Matic in a £40m deal to their bitter rivals Manchester United in 2016.
Willian ended the season out of favour under Antonio Conte after he started from the bench in the FA Cup final.
The Brazilian forward came off the bench for the final minutes of their 1-0 win against Manchester United at Wembley.
Former Shakhtar Donetsk star Willian won the Premier League title and the League Cup under Mourinho at Chelsea in 2014-15.
Sky Sports News reporter Sheth shed light on Mourinho’s interest in the South American forward.
“Jose loves him,” Sheth told the Transfer Talk podcast. “weHe bought Willian to Chelsea under the noses of Spurs.
“In his final few months, Willian was the only one who escaped criticism in those toxic months. He sees him as an ally.
“He sees him as a Jose Mourinho player.”
Manchester United finished in second place in the Premier League table last season but 19 points behind champions Manchester City.
The Red Devils finished ahead of Chelsea FC, who missed out on a Champions League spot following a fifth-placed finish.
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