Leicester City are set to sign Denmark defender Jannik Vestergaard from fellow Premier League side Southampton.
A reported £15m deal has been agreed for the centre-back, 29, who joined in 2018 from Borussia Monchengladbach.
“He is doing the medical check, and, when that is done, then the deal is done,” said Saints boss Hasenhuttl.
“He will go to Leicester, then it is for us to replace him and this is what we will do in the future.”
Southampton begin their 2021-22 Premier League campaign at Everton on Saturday (15:00 BST), while Leicester host Wolves at the same time.
Foxes boss Brendan Rodgers will be without defender Wesley Fofana until next year after the Frenchman suffered a broken leg in a pre-season friendly against Villarreal last week.
Vestergaard, who has 29 international caps, featured in all six of Denmark’s games as they reached the semi-finals of the European Championship in July.