Frederic Antonetti's team finished sixth last season and lie fifth this term, a point above improving Marseille and eight off leaders Paris Saint-Germain.
The new-found wealth of PSG may mean the title is out of reach for Rennes but the flood of signings at the capital club has meant benefits for other Ligue 1 outfits.
Erding has been deemed surplus to requirements at the Parc des Princes so Champions League hopefuls Rennes have swooped to bring him in and boost their forward line, which has already managed a healthy 31 league goals in 20 matches.
"This is a club which is growing in power. I hope we can do even better than last season," Erding told reporters at his unveiling.
"The coach really wanted me and I think we share the same philosophy. He wanted a striker with my characteristics."
Rennes' general manager is expecting big things.
"We will see if he is a great coup. I hope so," he said.
Whether Antonetti will throw Erding into the deep end against Marseille after he failed to get any meaningful action for PSG in the first half of the season remains to be seen.
"I hope to already be in the squad," the French-Turkish player added.
Antonetti's mind could be swayed by the fact last term's runners-up Marseille are weakend by the likes of Andre and Jordan Ayew being away at the Africa Cup of Nations.
Rennes are level on points with Olympique Lyon, who host Dijon on Saturday when champions Lille in third entertain Saint-Etienne.
Leaders PSG have a tricky trip to mid-table Stade Brest on Saturday with second-placed Montpellier, three adrift, hoping to pounce on any slip-up when they travel to struggling Nice.
