The 29-year-old has been heavily linked with a switch away from Villa Park after emerging as one of the Netherlands' stand-out performers in this summer's World Cup.
A move to the South Coast has been mooted, with Koeman having worked with the defender at Feyenoord, and the Dutch coach admits that he is keen on a reunion with his "leader".
"Vlaar became one of the best Oranje defenders at us, at Feyenoord," the Saints boss told Helden.
"And, at the last World Cup, he became one of the best of the tournament. He's a perfect addition to every group and a real leader. I would really like to have him at Southampton."
Vlaar's contract with the Villans expires next summer.