Arsenal XI vs Sporting Lisbon: Predicted lineup, confirmed team news, injury latest for Europa League game
Midfielder Mohamed Elneny is also out with a knee injury, but it is unclear if Gabriel Jesus is match fit and in the squad.
Nketiah and Trossard’s absences mean that Gabriel Martinelli may have to lead the line, with Bukayo Saka and Emile Smith Rowe likely to play either side of him.
Reiss Nelson, who scored the winner at the weekend against Bournemouth, is also pushing to start.
Goalkeeper Matt Turner should come in for Aaron Ramsdale, while Takehiro Tomiyasu may start in the absence of Tierney.
Jorginho is due to replace Thomas Partey at the base of midfield and Granit Xhaka is primed to play after being rested against Bournemouth.
Arsenal likely XI (4-3-3): Turner; White, Holding, Gabriel, Tomiyasu; Odegaard, Jorginho, Xhaka; Saka, Martinelli, Smith Rowe
Thursday 5.45pm GMT, BT Sport
Venue: Estádio José Alvalade
Referee: Tobias Stieler
Arsenal squad from: Hein, Ramsdale, Turner; Gabriel, Holding, Kiwior, Saliba, Tomiyasu, White, Zinchenko; Odegaard, Partey, Saka, Smith Rowe, Vieira, Xhaka; Jesus, Martinelli, Nelson.
Injured: Elneny (knee), Nketiah (ankle), Tierney (ill), Trossard (groin)
Doubts: Jesus (knee)