Christopher Nkunku will arrive at Stamford Bridge this summer on a pre-contract deal.
The Blues reportedly agreed on a deal of £53million deal to sign the Frenchman back in December.
Chelsea owner Todd Boehly expects the 25-year-old could solve the squad’s major attacking woes this season.
Nkunku, on the other hand, has struggled with injuries this season and was out of the World Cup squad.
Despite that, the attacking midfielder has still managed to score 17 goals from 28 appearances.
But former Man United manager Ralf Rangnick believes Nkunku made a wrong decision to move to Chelsea who are languishing 11th in the league table.
He told BILD: ‘I’m also thinking of a player whose arrival at RB Leipzig I was a little bit involved in: Christopher Nkunku.
‘For me, one of the best attacking midfielders currently available and who, in my opinion, decided to move to Chelsea far too early.
‘Can you imagine that such an outstanding player comes to a club that is in the state Chelsea are in at the moment?
‘Personally, this hurts my heart. If I were his advisor or his father, I would be very worried right now.’