QPR are have agreed a fee with Cardiff for Steven Caulker, who has been linked with Saints.
Former Tottenham centre-back Caulker, rated at some £8million, is a target for the newly-promoted Hoops, but the Cardiff captain, 22, is also attracting interest from the likes of Liverpool, Everton and Saints.
New boss Ronald Koeman could be in the market for a new centre half if wantaway defender DEjan Lovren joins the St Mary's exodus to Anfield.
QPR boss Harry Redknapp said of Caulker: We've agreed a fee with Cardiff and it's now up to Steven to decide his next move.
"I know him well from Spurs and he's always been a tremendous prospect. Hopefully that's another one we can get done."