Chelsea manager Jose Mourinho has confirmed that midfielder Frank Lampard and defender Branislav Ivanovic will be out for a month through injury.
The Serbian picked up a knee injury during Saturday's 2-1 win over Liverpool, while the England international sustained muscle damage during the same match.
The pair will miss this weekend's FA Cup clash with Derby County, as well the Premier League fixtures against Hull City, Manchester United and West Ham United.
Chelsea were in Premier League action on New Year's Day, defeating Southampton 3-0 away from home.