Liverpool defender Dejan Lovren could be out for up to three weeks with a pelvis injury, according to manager Jurgen Klopp.
The issue, which Lovren was able to manage last season, was aggravated as the centre-back carried a heavy workload playing for Croatia at the World Cup.
Lovren was a mainstay as Croatia were forced to play extra-time for three consecutive matches, before losing to France in the final.
"He is not fit," Klopp said. "Let me say it like this, last year he already had a few problems with that but he could obviously play - and played really good.
"Recovery days were always enough then it was not a problem and he was in the next session again. We did not train a lot in the end of the season, of course, because we were more or less constantly playing, but he played constantly.
"Now in the World Cup, [playing] three times [for] 120 minutes it got a bit worse, but I am pretty sure it will settle in the next one, two or three weeks. In that time he can probably for sure train already, but not the full programme, so that will then take time."
Liverpool coped just fine without Lovren on Sunday, as Klopp's side started their Premier League campaign with a 4-0 victory over West Ham at Anfield.
Joe Gomez delivered an assured performance as he filled in alongside Virgil van Dijk at the centre of the Reds' defence.
Last season's golden boot winner Mohamed Salah opened the scoring before a Sadio Mane double and late Daniel Sturridge tap-in put Liverpool top of the league following the opening weekend.
Their second game of the season will be live on Sky Sports as they travel to Selhurst Park to face Crystal Palace next Monday.