The 25-year-old has emerged as Chelseas first-choice left-back under Lampard this season but suffered a thigh injury during Italys win over Finland last month.
After missing Chelseas matches against Wolves and Valencia, Emerson was recalled for the visit of Liverpool at the weekend but he lasted only 15 minutes before being forced off.
Lampard has confirmed that Emerson suffered a re-occurrence of the same injury and wont be available for selection again until after the upcoming international break in two weeks time.
Speaking ahead of Chelseas Carabao Cup game against Grimbsy Town, Lampard said: Emerson now wont be back until the other side of the international break [which is during mid-October].
It will be a few weeks because it is the reoccurrence of an injury so we have to be a bit careful with it.
Emerson wasnt Chelseas only injury victim against Liverpool as centre-back Andreas Christensen also had to be replaced in the first half, shortly after Roberto Firmino had put Liverpool 2-0 up.