The Dutchman will not recover in time to make the Feb. 26 Wembley clash with Manchester United, leaving Saints exposed at the back.
Van Dijk, who picked up the knock during Southampton's 3-0 victory over Leicester City last month, will be out for two to three months, Puel said.
Southampton sold captain and central defender Jose Fonte to West Ham two weeks ago, leaving Saints thin on cover with only Japanese international Maya Yoshida and Romanian Florin Gardos as experienced options.
While the south coast side added Italy international striker Manolo Gabbiadini to their squad this week, Puel was not able to sign defensive cover before the transfer window closed.
"It's an important problem and difficult for us. He (van Dijk) is important for the group and the fans with his quality and leadership," Puel said.
"It's a blow but we will find a solution. For the semi-final second leg against Liverpool we got a fantastic result without him and we will continue with other possibilities."
Southampton beat Liverpool 1-0 both home and away in the semis to book their first major Wembley final since losing to Nottingham Forest in the 1979 League Cup final.
Their only major trophy to date remains the 1976 FA Cup, when they beat Manchester United in the final.
(Reporting by Shravanth Vijayakumar in Bengaluru; Editing by Ossian Shine)
Share
