The Holland international is shining in preseason for Saints, but is eager to return home for the new season.
"I do not want to deny that we are investigating whether Clasie can come in. Of course we know him as a child of the club, he could be of great added value," said Van Geel.
Saints signed Clasie three years ago for €15m and he spent last season on-loan in Belgium with Club Brugge.
The Premier League will have to accept a loss on Clasie's sale if he is to leave St Mary's this summer.