The Blues had been looking to append the 28-year-old Senegalese’s signature in what has been a big spending spree for them this summer, following a Fifa-imposed transfer ban in the previous two windows.
Mendy comes in to provide competition for Chelsea number one Kepa Arrizabalaga who has often been a shadow of the world’s most expensive goalkeeper that he is after his £71.6 million move from Athletic Bilbao in 2018.
Stephan asserts the timing of Mendy’s departure was not ideal, particularly as they will get to participate in the Champions League for the first time in their history this season.
The French tactician, however, insists the Brittany outfit must adapt.
He has also identified getting a centre-back as a priority having already signed one in Morocco international Nayef Aguerd from Dijon. Franco-Guinean striker Serhou Guirassy was also purchased from Amiens.
“There are different options, we let the sporting director [Florian Maurice] and the president [Nicolas Holveck] work on that, they work very hard. We knew that it was not the best timing for us, in this case, we have to adapt to the situation and everyone is working together to find the best possible option,” Stephan said at a press briefing.
“My priority is to fill the positions that we need to fill today, namely a goalkeeper and a central defender. Then if there is an opportunity to have an additional player in another department of the team, we will look, but the priority are these two positions."
Rennes have started well in the new Ligue 1 season, unbeaten after four games with three wins and one draw. They started off with a 1-1 draw at Lille, when both sides had a man sent off before sealing a 2-1 win over Montpellier in their first home match, both sides again finishing with 10 men.
They could claim top spot should they see off Saint-Etienne at Stade Geoffroy-Guichard on Saturday.