Rennes beat Emery's side 3-1 at Roazhon Park last night.
And former Newcastle United forward Ben Arfa impressed in the Europa League last-16 tie.
Ben Arfa was frozen out at Paris Saint-Germain by Emery, and the 32-year-old admitted he laughed at his"agitated" former manager – who succeeded Arsene Wenger at Arsenal last summer – during the game.
"My motivation was to play a solid match, to win and get ourselves into a good position to go through," said Ben Arfa.
"That's what was in my head. But I did see the same Emery, as agitated as ever. I looked over at him a few times and that made me laugh a little. He hasn't changed.
"I told some friends before the match that my prediction was that we would win 3-1 or 4-1. We didn't manage to get the fourth but my prediction was right."
The return leg will be staged at the Emirates Stadium next week.
"Arsenal are still the favourites," said Ben Arfa. "We will have to score at least one, maybe two goals.
"To be the first team to beat Arsenal in France (means) we are making our own history. I'm happy and proud to make people happy (but there) is a return match."
Ben Arfa was released by Newcastle four years ago after falling out with then-manager Alan Pardew.