Gabon worldwide Aubameyang opened the scoring in the fifth minute then settled nerves at Emirates Stadium with the Gunners' third goal in the second half.
"This comeback was very hard, but I think the reaction was very good from every player", Emery told reporters.
It's hardly surprising that Emery has maintained the shape that was fruitful against Manchester United as Arsenal require goals tonight against Rennes.
Rennes tactics on the other hand simply seemed to be a desire to get an Arsenal player sent off just like last week when Sokratis saw red for tangling with Ismalia Sarr.
Arsenal have become the sixth Premier League team to move ahead to the next stage of a European competition after they beat Rennais at the Emirates Stadium.
Arsenal hosted Rennes in the second leg of the Europa League last 16 on Thursday night looking to overturn a 3-1 deficit.
He also took note of surprising results elsewhere.
The Rennes boss Julien Stephan told this correspondent last week after the match at Roazhon Park in deepest Brittany that his team were facing a hard evening at the Emirates in the second leg.
"We are going to think the same before every match".