Liverpool manager Jurgen Klopp faces an anxious wait to discover the extent of the injury suffered by his key midfielder Fabinho in Wednesday's 1-1 Champions League draw against Napoli.
The Brazilian holding midfielder hobbled off in the 19th minute with an ankle injury, being replaced by Dutchman Georgino Wijnaldum.
"The biggest things is the Fabinho injury, that's massive," said Klopp.
"It's early and we all hope it's not too serious but it's pretty painful and in an area you don't want to have pain, around the ankle," added the German.
Asked by reporters how serious the injury could be, Klopp said: "I don't want to say what I expect because I hope it is not serious. He has pain, which is not good. He couldn't continue. I hope it is not that serious. We'll know more maybe tomorrow or the day after."
Liverpool are entering a vital phase of the season with 10 games before the end of the year, including the trip to Salzburg in the final Champions League Group E fixture where the European champions need at least a point to progress to the last 16.
Fabinho has become essential to the way Klopp's side play and there is no real like-for-like replacement for him in the squad.
The busy December fixture list also sees the Premier League leaders playing two games in the Club World Cup in Qatar.
Reflecting on the match itself, Klopp told BT Sport 2: "The one thing we couldn't do with the way Napoli set up was to concede a goal. It didn't help really and they could follow their plan all the time and we had to increase pressure.
"We didn't have the biggest chances, maybe one or two, they had some."
Klopp, in his 100th match as a manager in European competition, was cautioned during the first half.
When asked on why he got booked, Klopp added: "'Don't do that!’ That's what I said. He stopped the game twice and made a big fuss out of the situation."
Liverpool captain Jordan Henderson was disappointed not to see his side seal their place in the knockout stage of the competition, but remained confident that the defeating champions will progress.
"We would have liked to have won tonight and finish the job off but Napoli are a good side and made it difficult," he admitted.