Players are returning from injury
The Gunners have been extremely unlucky with injuries but come the first leg on 16th February, Arsenal could have a lot of players back who would be fresh to take on Barcelona. Coquelin, Wilshere and Cazorla could well be back against the Catalan club, which would be a major boost for the club.
Arsenal have had to deal with a ton of injuries but these players coming back would certainly strengthen them and prepare them for the battle that is against one of the most feared attacks in the world. Barcelona probably won’t even know what they are dealing with, they might not have the squad depth that Arsenal have but they do have a better first XI than the Gunners.