Southampton manager Claude Puel expects Virgil van Dijk to be out for two to three months with an ankle injury, meaning the Netherlands defender will miss the EFL Cup final against Manchester United.
Earlier this week, Puel said Van Dijk would be absent for "weeks" and has now confirmed the player he appointed as captain following Jose Fonte's move to West Ham will not be involved when Saints travel to Wembley on February 26.
Van Dijk suffered his injury following a challenge from Jamie Vardy in a 3-0 win over Leicester City last month.
The 25-year-old has made 30 appearances in all competitions for Southampton this season, scoring four goals, and his displays have seen him linked to the likes of Manchester City and Chelsea.
Puel told a news conference ahead of Saturday's game with West Ham: "Van Dijk will stay unavailable for many weeks – two or three months.
"I don't know how many times he will stay out but it is an important problem, and it is difficult for us."
Southampton now find themselves short at centre-back, with Fonte having joined their weekend opponents, although Puel is confident he can find flexibility within his squad to cope without Van Dijk and suggested left-back Ryan Bertrand could be deployed in the heart of defence.
"We will find a solution," he said. "He did not play the [semi-final] second leg against Liverpool and we got a fantastic result. We will continue to develop other players, other possibilities.
"[Ryan] Bertrand can play in this position. Then you have other young players like [Jack] Stevens – all the possibilities. We can find another solution, of course."
Van Dijk's sought-after status led to a question over whether the ex-Celtic man might have played his last game for Southampton, but it was a prospect Puel would not entertain.
"It's not the reality," he added. "I think he is an important player for us, it is an injury that's difficult for us, but the other things are just speculation."