(REUTERS) - Chelsea midfielder Frank Lampard and defender Branislav Ivanovic will be out of action until the end of January, the Chelsea website reported on Wednesday, Jan 1, 2014.

Following a 3-0 Premier League win at Southampton that left his side two points behind leaders Arsenal, manager Jose Mourinho said the injuries they sustained in Saturday's 2-1 home win over Liverpool would rule the pair out for about a month.

Serbian Ivanovic suffered a knee injury and was substituted in the first half while England international Lampard sustained a muscle injury and did not come out for the second half.

They will miss Sunday's FA Cup third round tie at Derby County before Chelsea play league games at Hull City and at home to Manchester United and West Ham United later this month.