The Blues winger has fallen out of favour somewhat under Antonio Conte.
Ex-Barcelona forward Pedro has replaced the Brazil international as a regular on the right side of Chelsea’s attack.
Last season under Mourinho before his sacking at Stamford Bridge, Willian was the Blues’ standout performer in a poor campaign.
However, the arrival of Conte has seen him fail to play a full 90 minutes of Premier League football this term.
Willian has struggled to nail down a place in Antonio Conte's Chelsea team this season
Mourinho is keeping an eye on Willian’s potential availability
And according to the Daily Star, Mourinho is keeping an eye on Willian’s potential availability, which may see the pair reunited.
Chelsea and Willian travel to Old Trafford today (4pm) for their showdown with Manchester United.
A victory will go a long way to securing title glory for Conte’s side, although Willian is not expected to start once again.
The 28-year-old has only been named in Chelsea’s first XI 13 times in the league this season.
Manchester United boss Jose Mourinho worked closely with Willian at Chelsea Chelsea line-up predicted to face Manchester United Wed, April 12, 2017
Click through the gallery for the predicted Chelsea line-up to face Manchester United
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Click through the gallery for the predicted Chelsea team to face Man United
Having lost his place, Willian may consider his future in west London, with Conte expected to strengthen his squad further this summer too.
Mourinho wants to bolster his attacking talent at United, and Willian is being considered as an option to target.
Convincing Chelsea to sell a star player to their direct rivals is likely prove difficult, though.