Liverpool midfielder Lucas has been ruled out for two to three months with a thigh injury, manager Brendan Rodgers said Wednesday.
The Brazil international suffered the injury in the opening minutes of Sunday's Barclays Premier League draw with Manchester City at Anfield.
It is a fresh blow for the 25-year-old, who had won his place back in the side after missing most of last season following knee surgery.
"It is very unfortunate. He has worked ever so hard to come back and he has been an outstanding player for me and person off the field as well," Rodgers said. "The indications are two to three months. It is quite a unique injury at the top of his right thigh."
Rodgers, however, is confident after seeing Lucas' response to last year's troubles that he can return to action quickly.
"He's a quick healer so I would hope we would have him back quicker than that, but we won't be rushing him," Rodgers said. "He is a very courageous guy and very focused. His aim is to get back as quick as he possibly can."
Rodgers said Lucas would see a specialist later Wednesday, the results of which will determine whether the midfielder needs surgery or can return after rehabilitation.
Lucas posted a message on Twitter on Wednesday after Rodgers' announcement.
He wrote: "No words to describe my feelings at the moment. It has been hard to be positive but I am sure better days will come. YNWA."
Lucas' injury could allow an opportunity for new loan signing Nuri Sahin, brought in on a one-year deal from Real Madrid, to make his debut against Arsenal this weekend.
The Turkey international is ineligible for the Europa League qualifying round playoff second leg against Hearts.
Information from Press Association was used in this report.