Barcelona chief Robert Fernandez had scouts at the Emirates on Sunday.
El Mundo Deportivo says Fernandez's reps saw Arsenal thump Manchester United 3-0.
Gunners defenders Gabriel and Hector Bellerin were on their radar.
Bellerin, 20, quit Barca's youth set-up to join Arsenal back in 2011, while Gabriel signed for the club in January from Villarreal.
Scouts were also looking at Wales international Aaron Ramsey, while they ran the rule over United's Ander Herrera, Daley Blind and summer signings Matteo Darmian and Memphis Depay.