Sadio Mane looks set to miss Liverpool's match against Bournemouth on Wednesday after suffering a knee injury during their 3-1 victory over Everton.
The Senegal forward scored an early goal as Jurgen Klopp's side strengthened their hopes of Champions League qualification with a deserved win in the 228th Merseyside derby at Anfield on Saturday.
He limped off in the second half following a collision with Everton defender Leighton Baines, but did not leave the ground on crutches, giving Liverpool hope he will not be out for long.
"Today nearly everything was perfect, then we lose Sadio Mane," said Liverpool manager Klopp.
"When I saw him in the dressing room, it didn't look as if he would be ready for Wednesday. We will see. We hope it's not that serious, but it does not make our life easier."
Klopp added: "Obviously he has pain and it didn't look like it's only a knock or a muscle or something, but we have to wait."
Divock Origi, who replaced Mane, scored the third goal, with Philippe Coutinho's superb shot having made it 2-1 at half-time after Matthew Pennington's first senior goal briefly brought Everton level.
Klopp was diplomatic when asked to comment on some controversial tackling from Everton's Ross Barkley.
The England midfielder, already on a booking, was fortunate to stay on the pitch for a reckless first-half lunge into the shins of Liverpool defender Dejan Lovren.
"It's not my job to say about tackles," Klopp said. "If I do, I create a story: 'Klopp says...' If you think it was a problem, then speak about it."
The Liverpool manager was more happy to discuss the quality of his team's performance.
- Liverpool 'show' angers Koeman -
"It was a deserved victory," said the German. "We controlled the ball after the first few minutes. I told the boys to be really smart and emotional.
"The last 20 minutes were a bit wild. When organisation doesn't work any more, you have to defend with passion."
Victory provisionally lifted Liverpool to third place, with Everton nine points below them in seventh place.
Everton manager Ronald Koeman was angry about the way Liverpool's coaching staff reacted to Barkley's tackling.
Koeman suggested Klopp and his staff wanted "eight red cards" for Everton players.
The Dutchman expressed pride in his side's performance, but said the Liverpool bench needed to "behave a little bit more".
Asked if Barkley deserved to be sent off, Koeman said: "Maybe you are right that Ross Barkley deserved two yellows.
"But if I watch the Liverpool bench –- not the manager, but one of the coaches -– the referee would have to show eight red cards to Everton.
"Please behave a little bit more. Making that show, I don't like that."
Everton were second-best for most of the match, yet Koeman defended the display of his players.
"I am really proud about my team. What pleased the manager is how we played," he said.
"We had a game plan. We tried to press them. We made it really difficult. We came back after an unlucky goal, a good goal, but an unlucky goal between the legs, which is always difficult for the goalkeeper.
"I think we controlled the game."