Only 2 players from Arsenal were regular internationals from World Cup participating sides, and one of them was a goalkeeper and the other was someone who joined less than a month ago. Iwobi is not yet a regular and Egypt is Egypt. A disjointed performance was to be expected: although not that bad. Yet, they did show up eventually. I think these things actually happen to all teams who set up to defend a sizable first leg lead. I mean last year PSG let in 6 goals! in the second leg after destroying Barcelona in the first leg.