Newcastle United fear that Fabricio Coloccini will miss the rest of the season.
The relegation-threatened club’s captain has been sidelined since February with a calf problem.
Coloccini had been close to a comeback, but he suffered a setback earlier this month.
And United manager Rafa Benitez “not optimistic” that Coloccini will play any part in the final four games of the campaign.
Asked if he would play again this season, Benitez said: “I hope so.
“But the setback was worse than I was expecting. I am not very optimistic at the moment.”
Coloccini – who signed an extension to his contract keeping him at St James’s Park until the summer of 2017 on the eve of the campaign – broke down after “pushing hard” to return.
The 34-year-old defender said: “I am desperate to come back, so was pushing as hard as possible.
“Maybe it was too fast, but that was my decision because I wanted to be early and ahead of schedule.
“Now I have to take more time, but I am still trying to get fit as soon as possible so I can get out on the pitch and help the team in the final games.”
In his absence, Jamaal Lascelles has come to the fore at Newcastle.
The 22-year-old defender has shown leadership on and off the pitch in recent weeks.
And Lascelles has impressed Benitez, whose second-bottom side take on his former club Liverpool at Anfield this afternoon.
“From watching from outside, you can see a young centre-back who normally needs to improve and make mistakes,” said Benitez.
“But the reaction when he makes mistakes when we are training ... he is always listening to you and tries to understand.
“He is doing really well, and he will be a really good centre-back for the future because he is doing really well now and he is learning.
“He is so young for a centre-back – (he) still has 10 years to play at the maximum level.
“I can see someone who is very professional, who is keen to learn, and for a centre-back he has a great future.”