When the Gunners brought him in to succeed Arsene Wenger, they knew he was facing a rebuilding job and that instant success might have to wait.
When we sat down earlier this season with Raul Sanllehi and Vinai Venkatesham, who were instrumental in appointing him, they were clear on that.
Both of them were at pains to stress that a team which finished 37 points behind champions Manchester City was not suddenly going to win the league.
The Gunners need to be back in the Champions League as quickly as possible. Every year they fail to make it is another year of lost revenue.
If they ever want to be competing for the truly world class players who could help make them champions again, they must get back to Europe’s top table.
There is no suggestion that Emery could be sacked if he fails to achieve that this season. But doubts might start to creep in if he loses badly tonight.
Arsenal expected to beat Rennes. They had a disaster in the first leg only because Sokratis got sent off. They have enough firepower to overturn a 3-1 deficit and go through.
They go into the game on an eight-match winning run at home and on the back of a convincing win over Manchester United that will give them huge confidence.
Failure is not an option.
This year’s top four race looks tighter than ever – and depending who wins the two European trophies this season there is no guarantee that fourth place will get you into the Champions League.
So winning the Europa League, the way United did under Mourinho two years ago, might very well be their best shot at getting back into European football’s top club competition.
Emery knows how to do it. He won it three times in a row with Sevilla. But as he said to us this week: “The past does not exist. Only the present and future.”
Arsenal have been up and down this season. They looked like also-rans when they opened the campaign losing to Manchester City and Chelsea.