The Portuguese manager was let go after the 3-1 defeat at the hands of Liverpool, and the report claims that he learned about the move for Costa just before he was removed from the club.
The report adds that Ed Woodward would be pressing ahead and signing a central defender, something that Mourinho wanted, in the winter window too.
Costa has found it difficult to get regular starts at Juventus after the arrival of Cristiano Ronaldo from Real Madrid.
The 28-year-old Brazilian has only four starts for the Old Lady this season and hasn’t scored or assisted any goals this term either.
The report adds that signing a forward in the winter window is a priority for our struggling attack, and the Brazilian is the player they want.
The 28-year-old was great for the Italian side after performing well during a loan spell, but things have gone south for the winger.
United could offer him an escape in the winter window, and it will be interesting to see who else we try to sign in January.
Ole Gunnar Solskjaer has been named as the interim manager till the end of the season, and the former United star has a big job on his hands if we are to somehow save this campaign.