Nketiah was not spotted in team training with the Gunners on Tuesday, having apparently sustained a knock during the weekend's Premier League defeat to Newcastle United.
The 24-year-old's affliction is serious enough to keep him out of the Group B encounter, as Trossard joins Bukayo Saka and Gabriel Martinelli up front in the only change from the loss at St James' Park.
Mikel Arteta's side also remain without Martin Odegaard due to a fitness issue, allowing Kai Havertz to continue alongside Jorginho and Declan Rice in the midfield trident.
Takehiro Tomiyasu is again given the nod on the left-hand side of the backline ahead of Oleksandr Zinchenko, while Aaron Ramsdale continues his wait for his Champions League debut as David Raya continues in goal.
Meanwhile, Sevilla boss Diego Alonso has sprung a few surprises in his selection, dropping Jesus Navas, Lucas Ocampos and Boubakary Soumare to the bench as Erik Lamela, Joan Jordan and Juanlu Sanchez make the XI.
However, there is an expected recall up front for Youssef En-Nesyri, while Sergio Ramos is absent through injury.
Arsenal: Raya; White, Saliba, Gabriel, Tomiyasu; Havertz, Jorginho, Rice; Saka, Trossard, Martinelli
Subs: Ramsdale, Zinchenko, Kiwior, Vieira, Nelson, Hein, Cedric, Elneny, Cozier-Duberry, Sagoe Jr
Sevilla: Dmitrovic; Juanlu, Bade, Gudelj, Salas; Jordan, Fernando, Sow; Lamela, En-Nesyri, Pedrosa
Subs: Flores, Gattoni, Ocampos, Suso, Mir, Rakitic, Lukebakio, Diaz, Nianzou, Navas, Torres, Soumare