Liverpool fear defender Sotiris Kyrgiakos could be set for a lengthy spell on the sidelines with a knee injury.
The Greece international, who joined the Reds from AEK Athens in August, was forced off just before half-time in his country's 2-1 World Cup qualifying win over Luxembourg on Wednesday night.
The 30-year-old went straight to hospital for an MRI scan on his knee and early indications are that he could have ruptured his anterior cruciate ligament.
Recovery from such an injury can take four months but may take as long as six, meaning Kyrgiakos will definitely miss Greece's two-legged World Cup play-off in November.
That would also leave Liverpool short of defensive cover for first-choice centre-backs Jamie Carragher and Martin Skrtel.
Daniel Agger is yet to play for the Reds this season but has come through two games for Denmark this week, while Spanish rookie Daniel Ayala only made his debut in August.
Kyrgiakos was drafted in by manager Rafa Benitez to fill the void left by Sami Hyypia's departure for Bayer Leverkusen and the uncompromising centre-back has so far made just two appearances for the club.