Emerson will be out until mid-October after suffering a recurrence of his thigh injury during Chelsea's defeat to Liverpool on Sunday, Frank Lampard has confirmed.
The left-back, who was making his return after two games out with injury, was forced off after just 15 minutes at Stamford Bridge.
"Emerson now won't be back until the other side of the international break," Lampard told Chelsea's website.
"It will be a few weeks because it is the recurrence of an injury so we have to be a bit careful with it."
Emerson will miss Chelsea's Carabao Cup game against Grimsby on Wednesday as well as their Premier League fixture with Brighton on Saturday.
The 25-year-old is set to return against Newcastle on Saturday October 19, although Italy could yet call him into their squad for their European Qualifiers on October 12 and 15.
Lampard also provided an update on Andreas Christensen, who followed Emerson off the field against Liverpool after sustaining a knee injury.
The head coach said: "Andreas is not too severe. Hopefully he won't be out for too long but I can't give a timeframe."