Frank Lampard admits worry over players' long-term fitness due to packed fixture schedule; Chelsea play Rennes in the Champions League on Wednesday
Chelsea signed Mendy from the Ligue 1 side in September in a bid to help resolve their defensive issues, having finished with the worst defensive record of any top-10 Premier League team last season.
The 28-year-old has excelled since moving to Stamford Bridge, keeping five clean sheets and conceding just one goal in his six appearances, and Chelsea head coach Lampard has hailed his influence on and off the field.
He said: "When we looked to sign him, we obviously made enquiries. Petr Cech was heavily involved - I think that's pretty common knowledge.