The Portuguese manager was very complimentary towards the Cameroonian international.
Mourinho admitted that Onana had denied his team three points in the 1-1 Europa League draw on Thursday.
He stated on Onana being man of the match: "Come on! He saved the result! My goalkeeper didn't make a save, he made two impossible saves in 10 seconds. I think he is the most decisive player in the result. Of course, he didn't make 20 saves, but he made two saves... incredible."
And on Noussair Mazraoui playing as a no.10 instead of a full-back, he added: "He can (play there). The coach (Erik ten Hag) knows him well, the coach coached him at Ajax in that position.
“I understood what he was trying. (Joshua) Zirkzee is a striker I know very well from my Italian times, he is a striker that drops back all the time, attracting defenders or not, then the wingers attack the space. Mazraoui is a guy who can run, a guy that can attack the spaces. I know.”