James Beattie's sale will be worth at least £1m to former Saint Mark Hughes.
The welcome present for the manager of Beattie's former club Blackburn is down to a clause in his Saints contract, stating that the Ewood Park outfit will gain 20 per cent of any profit on the player, who cost £1m.
That means the 26-year-old's likely £6.5m move to either Aston Villa or Everton will see Saints' relegation rivals pocket £1.1m.
The Ewood Park outfit insisted on the sell-on clause when the then Saints boss Dave Jones took a 20-year-old Beattie to The Dell in the summer of 1998.
Jones became aware of Beattie after seeing his son play schools football with the Lancaster-born front man.
But, despite the sell-on clause, Beattie's sale will represent an impressive return with Saints set to gain a profit of more than £4m.
Aston Villa and Everton remain the favourites to sign Beattie but neither David O'Leary or David Moyes want to get involved in a bidding war, so the fee is unlikely to go past the £6.5m mark.
O'Leary is believed to want the charge brought against him for allegedly tapping up Beattie in the summer to be dropped before Villa move in.
O'Leary is due to appear before the FA on January 18 but Redknapp is hoping to complete a deal in the next few days.
He said: "By the time the end of January comes, you're well in trouble. In an ideal world, I'd have two or three in by Wednesday."
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