With first choice goalkeeper Manuel Almunia and back-up Łukasz Fabiański out injured, Mannone made his first UEFA Champions League start against Standard Liège, in Arsenal's first group stage match on 16 September 2009. Mannone's night got off to a poor start, conceding twice within the first five minutes: first from a shot from outside of the box by Eliaquim Mangala which beat Mannone at the near post and then a penalty converted by Milan Jovanovic after he was brought down by William Gallas. However, Arsenal recovered to win the match 3–2, after goals from Nicklas Bendtner, Thomas Vermaelen and Eduardo.