The attacker set up decisive goals in the last two Champions League games to ensure Arsenal progressed beyond the group stage and the coach says it convinced him of his quality.
Arsene Wenger has acknowledged that Joel Campbell's ability to shine under pressure in the Champions League helped save the attacker's Arsenal career.
The Costa Rica international joined Arsenal in 2011, but subsequently spent time on loan at Lorient, Betis, Olympiacos and Villarreal.
The Gunners have held onto the winger this season, though, and he has found playing time easier to come by.