The pair come in for Aaron Ramsey and Abou Diaby in just two changes from the side who lost 2-1 at home to Chelsea on Saturday, with Roy Carroll on the bench for the Greek side
Arsene Wenger has made just two changes from the team who lost 2-1 at home to Chelsea on Saturday as the Gunners look to build upon the win over Montpellier in matchday one.
The youngsters come in for Aaron Ramsey and Abou Diaby, with the latter having to withdraw after 20 minutes against the Blues with a thigh strain and is expected to remain out for three weeks.
Mikel Arteta was a doubt for the clash, but has passed a late fitness test to start against the Greek champions.
For Olympiakos, former Manchester United goalkeeper has to settle for a place on the bench as youngster Balazs retains his starting spot.
Arsenal: Mannone; Jenkinson, Koscielny, Vermaelen, Gibbs; Coquelin, Arteta; Oxlade-Chamberlain, Cazorla, Podolski; Gervinho.
Subs: Shea, Santos, Giroud, Walcott, Ramsey, Arshavin, Djourou
Olympiakos: Megyeri, Diakite, Manolas, Contreras, Holebas, Siovas, Maniatis, Greco, David Fuster, Paulo Machado, Mitroglou.
Subs: Carroll, Modesto, Ibagaza, Pantelic, Lykogiannis, Diogo, Abdoun.