Liverpool midfielder Lucas will be out for five to six weeks with a thigh injury, says manager Jurgen Klopp.
The Brazilian injured himself taking a penalty, which he missed, in the shootout as Liverpool lost the League Cup final to Manchester City on Sunday.
The 29-year-old missed Wednesday's 3-0 against City at Anfield in the Premier League.
Klopp also confirmed defender Mamadou Sakho and England striker Daniel Sturridge were back in training.
Both players missed Liverpool's midweek game at Anfield with Sakho suffering a head injury in the cup final defeat while Sturridge did not take a penalty.
Liverpool travel to Selhurst Park to play Crystal Palace in the Premier League on Sunday with kick off at 13:30 GMT.