Southampton are one of a number of Premier League clubs interested in Borussia Mochengladbach defender Jannik Vestergaard, according to Sky sources.
Sky Sports News understands initial talks between the clubs have focused on trying to agree a transfer fee.
West Ham are also thought to be interested in the 25-year-old, who was part of Denmark's World Cup squad in Russia.
He was an unused substitute in each of Denmark's four matches as they went out on penalties to Croatia in the last 16.
Vestergaard made 32 appearances in the Bundesliga last season, scoring three goals. He has played in Germany since 2011, where he has previously had spells with Hoffenheim and Weder Bremen.
Saints boss Mark Hughes has already made two signings this summer, bringing in winger Mohamed Elyounoussi from Basel and midfielder Stuart Armstrong from Celtic.