Tuchel and his Chelsea side will face one of the most in-form players in the Premier League when Manchester United visit Stamford Bridge on Sunday.
Fernandes swapped Sporting Lisbon for the red half of Manchester in January 2020 and has become one of the main reasons for the Red Devils’ rise up the table.
The 26-year-old Portuguese international has scored 15 goals and provided 10 assists in the top flight this season for United, who are second on the table and six points ahead of Chelsea in sixth.
Tuchel has been impressed with the impact Fernandes has had on Ole Gunnar Solskjaer’s side and says he made efforts to bring him to the Parc des Princes.
"With my first sporting director in Paris, Antero Henrique, a Portuguese sporting director, and he knew [Fernandes] very well," Tuchel told reporters.
"We fought hard to have a connection to him and to bring him to our team. I got made aware of him more in detail, so we watched more and more games about him and followed him and tried to be in touch with him to make it happen.
"Obviously, he decided [to sign for Manchester United] and I was never personally in touch with him, but we tried and he went another way. [It is] bad for us that we have to play against him."
"The impact he has had since he arrived at Manchester United is indescribable and unbelievable," Tuchel added.
"To come from Portugal, from a competitive team, a big club but not from the strongest league and stepping in a year to one of the biggest clubs in the Premier League and the strongest league in Europe and to have this kind of impact, I have nothing but the biggest respect for this guy.
"It is outstanding. He is one of the best midfielders in the world, attacking midfielders, and he has a huge, huge impact and to have this as a single person in football, you must be absolutely top level because this is almost impossible.
"But he has such a big influence on their game, on their attacking game and that it is a big key to defend against him, to be around him and close to him and he is a key player of Man Utd in a way that is outstanding."
