The mercurial talent of Hatem Ben Arfa has helped the mid-table Ligue 1 side reach the last 16 of a European competition for the first time.
Ben Arfa endured an unhappy two years under Emery at Paris Saint-Germain where he was frozen out for an entire season and made to train with the club's reserves.
However, at 31, Ben Arfa has relaunched his career in the more modest surroundings of Roazhon Park and will aim to inflict revenge upon Emery on Thursday.
Rennes may lie 10th in Ligue 1, but shocked a highly-fancied Real Betis in the last 32 with a thrilling 6-4 aggregate win.
"We know it'll be a level up against such a club," said Rennes midfielder Benjamin Andre. "Arsenal is a name that resonates throughout Europe. They will obviously be the big favourites."
Arsenal's struggles on the road in Emery's first season in charge should give the French side reason to believe.
The Gunners have won just once away from home since November, suffering an embarrassing 1-0 defeat to BATE Borisov in the last 32 before turning the tie around at the Emirates.
French international Alexandre Lacazette will miss out on a return to his homeland as he is suspended, but there will be a homecoming of another sort for Petr Cech, who spent two years at Rennes before joining Chelsea in 2004.