The Nigeria international returned from injury during Friday's 3-1 victory over Kasimpasa, making a substitute appearance after missing three consecutive matches.
Osimhen is now expected to start against the Spanish giants in their Matchday Two encounter.
Flick claimed the former Napoli forward's attacking qualities and warned that Barcelona must deliver their best performance to overcome the Turkish champions.
“Galatasaray have a fantastic striker like Osimhen. They really have a great squad. We need to be ready for this match. We have to play our best football against Galatasaray,” Flick was quoted by Ahaber.
