Jurgen Klopp will have to play a waiting game on Philippe Coutinho after the Liverpool playmaker was carried off on a stretcher against Sunderland.
The Merseysiders prevailed 2-0 thanks to a goal from Divock Origi - Coutinho's replacement in the first half - and an injury-time James Milner penalty.
But Coutinho's injury took the shine off the victory with the Brazil international leaving the stadium with his right foot in a protective boot, according to reports.
Klopp told a news conference: "We have to wait for the scan, it's something to do with his ankle. We all have to wait.
"He had pain but pain gets better. In the first moment it was very painful but when I saw him at half-time he said the pain was much better.
"I am quite an optimistic guy so I hope he can train tomorrow!"
A more realistic outcome is a spell on the sidelines but Klopp is hopeful he will not be accompanied by fellow forward Roberto Firmino, who limped off late on with a calf injury.
"He's much better than Phil," said Klopp, who also confirmed England striker Daniel Sturridge missed out against the Black Cats with a tight calf.
Coutinho's unfortunate withdrawal provided the chance for Origi to impress and he took it with both hands, his cross-shot finally ending Sunderland's stubborn resistance with 15 minutes to go.
"He deserved it," said Klopp. "It has not been easy for him but he's a very positive guy and is willing to learn. Today he got the benefit of that."
Former Borussia Dortmund boss Klopp was unimpressed by Sunderland's defensive approach, describing David Moyes' side as the "most defensive team I have ever played against".
"It's not for me to say what other teams are doing," he said. "But we forced them into this position, their plan was not that Victor Anichebe played left-back.
"We also pushed [right-back] Nathaniel Clyne into a higher position and that gave us space elsewhere. It meant the box was quite full and the more the space is closed the harder it gets.
"You need to stay patient and not allow yourself to get frustrated and then be ready for that one moment.
"What we are doing at the moment is a real challenge. We are ready to play teams like this but it's not easy. I saw some of Burnley versus Manchester City earlier and it didn't look easy for City either so it's a job for us all to do if you want to be in the top region of the table."
Moyes offered no apologies for his team's approach and rued Sunderland's inability to take the few chances that came their way.
"I thought we'd got to the point where it needed their manager to get the crowd going, we'd frustrated them for long periods," he said.
"It was always going to be difficult coming here, they've got a great attacking theory about them - they are probably the best attacking team in the Premier League at this time.
"We had to make sure we did our job defensively and try to create opportunities when we could and I thought we created a great chance at 0-0 for Duncan Watmore. You need to take it and we didn't, they're the small margins."
Defeat ended the Black Cats' mini revival that saw them record back-to-back wins against Bournemouth and Hull City.
"We had two great results recently but, in truth, the last place you want to come after that is Anfield so it was always going to be difficult," he added.
"We knew that but I thought the players did a great job in managing the game. In the end it wasn't good enough but the quality in the two squads would probably give you the reasons for that."
