Paris - Unai Emery's Arsenal cruised to a 3-0 victory away to Azeri champions Qarabag in the Europa League on Thursday, while Celtic slumped to a 3-1 defeat against Red Bull Salzburg.
Sokratis bundled in a Nacho Monreal header on four minutes in Baku, with Arsenal academy graduate Emile Smith Rowe and French youngster Matteo Guendouzi also scoring their first goals for the club.
The Gunners extended their winning run to eight matches and lead Sporting Lisbon on goal difference at the top of Group E, after the Portuguese side snatched a 2-1 win in Ukraine with two late goals against Vorskla Poltava.
Arsenal's Armenian midfielder Henrikh Mkhitaryan did not make the trip to Azerbaijan due to diplomatic tensions between the country and his homeland.
Odsonne Edouard fired Celtic ahead after just two minutes in Austria, but a brace from Munas Dabbur and a goal from Japanese forward Takumi Minamino gave Salzburg a second win in two Group B matches.
Celtic lost James Forrest to a straight red card after he upended Andreas Ulmer in the area, with Dabbur converting the resulting penalty to condemn Brendan Rodgers' side.
Seven-time European champions AC Milan recovered from a goal down at home to Olympiakos to claim a 3-1 victory in Group F, as Patrick Cutrone scored twice either side of a Gonzalo Higuain effort.
Steven Gerrard's Rangers are in action at home to Rapid Vienna in the later round of games, while Chelsea host Hungarian outfit Vidi at Stamford Bridge.