However, Chelsea’s opening £15m bid has been turned down so the Premier League side will have to come back with an improved offer if they are to snap up their target.
Mendy joined Rennes from Reims for just £3.6m last summer and is under contract until 2023 so the Ligue 1 outfit are set to make a healthy profit off any future transaction.
Meanwhile, Chelsea announced the signing of Ben Chilwell in a £50m transfer from Leicester on Wednesday and club director Marina Granovskaia is believed to be in negotiations with Bayer Leverkusen over a deal for Kai Havertz.
The Bundesliga side want £90m for the German international, but Chelsea were thought to initially value the attacker at around £70m.
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