Liverpool are waiting to discover the extent of midfielder Lucas Leiva's thigh injury amid concerns that he could be out for up to two months.
Lucas, came off five minutes into Sunday's 2-2 draw with Manchester City after having felt the injury during the warm-up.
Manager Brendan Rodgers initially thought the 25-year-old had pulled a muscle, but is worried that it could be a tear that would keep him out for between six and ten weeks.
Lucas missed the final five months of last season after damaging his cruciate knee ligament in a League Cup victory at Chelsea at the start of December.
He made his return to action earlier than expected during Liverpool's pre-season tour of North America in July, and is desperate to avoid another long spell out of action.
After suffering his injury on Sunday, the midfielder wrote on Twitter: "Thanks (for) all the message(s). I am devastated but I need to put my head right and see in the next few days how bad (it) was. Good night."
Lucas's misfortune is likely to give new signing Nuri Sahin a chance to make his debut against Arsenal at Anfield on Sunday.
Turkey international Sahin, 23, has moved to Anfield on a season's loan from Real Madrid.