Arsenal looked clueless against the relentless pressure put on them by the reigning champions and Aguero took full advantage of their defensive lapses to complete his second hat-trick of the season and lead his side to a very important win.
"His adaptation to us and also on Sunday in 25 minutes, in the first days with us, is not with good performance", Emery said.
Unai Emery insists he won't be affected by growing criticism of his Arsenal reign as the misfiring Gunners bid to get back on track at Huddersfield on Saturday.
Emery's team sit sixth - a point behind Manchester United and three behind Chelsea - but the Spaniard concedes it will be hard to guarantee Champions League football next season.
Nantes demand that Cardiff pay Emiliano Sala's transfer fee
Cardiff are reported to be committed to honouring the deal but not until they have been provided with sufficient documentation. A recovery crew eventually found the aircraft in the ocean, with a body said to be visible in the wreckage.
Emery admitted he is his own biggest critic as he spoke at a news conference on Thursday, but remained confident his team can return to winning ways against Huddersfield, who are bottom of the Premier League and have won just two matches all season. We are strong at home but we need to do better away. That shows the significance of Lacazette in the side, and the striker has to further stamp his authority in games like Huddersfield, and these are games where three points matter and three points here will go on to help Arsenal in the top four race.
"One month ago we were in the same situation". The Gunners, like last season, have endured a hard time away from home, winning their last game outside of the Emirates on November 25th. "But after this week, playing with the under-23s and working with us, I think it is the first time I can think about him being with us".
"We know that defensively we need to do better".
Emery said: 'He wanted to stay and work with us.
"I hope he will continue, he is improving every day with us. For us as well, away games have been a challenge and each match is a new challenge".