Losing Osimhen had a huge impact on Napoli in the last two matches against AC Milan. They lost 0-4 in Serie A and lost 1-0 in UCL which indicates that Osimhen really has a big impact on Napoli front line. Elmas or Lozano have not been able to give their best for Napoli in the match. They were not impressive enough in the final finish, it was even difficult for them to make AC Milan bottom line difficult in the match.
Osimhen is important for Napoli because his contribution is very diversifying. He can score goals for them but he is a striker who is ready to do pressing task in the front line which can help Napoli to reduce pressure from opponents. Especially it can help them to reduce risk of counter attacking from opponent or at least reduce its speed of counter attack.
One more contribution is he can connect well with Kravatskhelia and those players will help other players have more space to play when opponents will spend most of their focus on those two best attacking players of Napoli.
Maybe the second leg will be good enough for Napoli because there is already a green light if Osimhen will play in the second leg later. But I doubt with his performance whether he can quickly find his best form after he recovers from injury.
I am not sure will Osimhen get his best fitness and ability to play shortly after his recovery from the injury. Have him in a squad is better than without him but we have to wait for the match to see the performance of Osimhem.
Losing by one goal in a first leg is not the end for Napoli. They have a comfortable task, beating AC Milan with a same result to continue it in extra half. However in the second leg, they will figure out how to control Rafael Leao better.