The pair had initially been doubts for the game, but both have recovered in time and are now set to start.
Nicolas Pepe may hope to start instead after impressing against Sheffield United on Sunday or Willian could return to the team.
Martin Odegaard (ankle) and Pierre-Emerick Aubameyang (illness) are doubts for the game in Prague, which Arsenal go into trailing on away goals after drawing the first leg at Emirates Stadium 1-1.
David Luiz and Kieran Tierney will both definitely miss out due to knee issues.
Arsenal likely XI: Leno; Bellerin, Holding, Gabriel, Cedric; Partey, Xhaka; Saka, Smith Rowe, Pepe; Lacazette.
Thursday 8.00pm GMT, BT Sport
Arsenal squad from: Leno, Ryan; Bellerin, Cedric, Chambers, Gabriel, Holding, Mari; Ceballos, Elneny, Odegaard, Partey, Saka, Smith Rowe, Xhaka; Aubameyang, Balogun, Lacazette, Martinelli, Nelson, Nketiah, Pepe and Willian.
Doubts: Aubameyang (ill), Odegaard (ankle)
Injured: Luiz (knee), Tierney (knee)