Kalidou Koulibaly picked up the injury after pulling up while sprinting in the second half against Real Madrid and he was replaced by Marc Cucurella.
Chelsea's Koulibaly out for weeks
The Senegal international will not be available for this weekend's Premier League clash with Brighton and he will also miss the return leg against Los Blancos next week.
"He won't be available for either game. A matter of weeks rather than days." Lampard said
"He's a very good, very experienced player. People talk a lot about our squad, Champions League squad is different to Premier League and a disappointment but also an opportunity."
More on Chelsea
England stars Mason Mount, Conor Gallagher and Ruben Loftus-Cheek could all depart Stamford Bridge in the summer. The other players who could leave the club are N'Golo Kante, Mateo Kovacic, Hakim Ziyech and Pierre-Emerick Aubameyang.
Chelsea are back in Premier League action this weekend when they face high-flying Brighton at Stamford Bridge.