Scans have confirmed Liverpool midfielder has Thiago Alcantara suffered a hamstring strain, it is understood.
The Spain international will now face a spell on the sidelines but the club are hoping the problem is not serious and he could return to action within weeks.
The 31-year-old was forced off early in the second half of the Reds' opening Premier League match of the new season at Fulham last Saturday.
No timeframe has yet been put on his return and he will undergo another scan later this week to determine the extent of the problem.
His absence will be a blow for manager Jurgen Klopp, with Curtis Jones, Diogo Jota and Alex Oxlade-Chamberlain already on the injury list.
Liverpool host Crystal Palace in their second Premier League game on Monday before travelling to Manchester United the following week.
The Reds drew 2-2 at Craven Cottage in their opener after twice coming from behind.
Meanwhile, Newcastle midfielder Jonjo Shelvey is facing up to three months on the sidelines after undergoing surgery to address a hamstring injury.
It is believed that 30-year-old Shelvey will be out of action for around 12 weeks following the procedure at the weekend.
That means he could be unavailable to head coach Eddie Howe until St Stephen's Day at the earliest, with the Premier League breaking in mid-November for the World Cup finals.
Shelvey, who had returned to Tyneside following his summer break in excellent shape after working with a personal trainer in Turkey, suffered the injury during the club's friendly defeat by Benfica in Portugal on 26 July.
The development will come as a major blow to a man who revealed during the closed season that he needs to make just three more senior appearances to trigger a contract extension.
Shelvey was a key member of the side who fought their way to Premier League safety under Howe last season having forced his way back into the team in the wake of Steve Bruce’s departure.
The excellence of January signing Bruno Guimaraes and Sean Longstaff’s return to form will mitigate his absence to an extent, but the variety provided by a midfielder described at the weekend by Howe as "unique" will be missed.
Shelvey’s misfortune may cement 19-year-old Elliot Anderson’s place in the squad at St James’ Park, with the prospect of another loan move after his hugely successful spell at Bristol Rovers last season seemingly having receded further.