Bradley Wright-Phillips has signed a three-year deal at St Mary’s after moving from Manchester City for an undisclosed fee.
However £250,000 of that will be paid by Championship sponsors Coca-Cola as the prize money won by the club in a recent competition.
The rules allow the winners to buy a player for a quarter of a million or to put the money towards a larger fee.
And Saints have opted to use their Coca-Cola cash to buy the 21-year-old half brother of Chelsea winger Shaun Wright-Phillips. He scored his first goal for the club in the opening day 2-2 draw at Derby.
The England Under 20 international made a total of 32 Premiership appearances for City - 31 of them from the bench.
He netted two goals, including one within three minutes of coming on for his debut against Middlesbrough in December 2004.
His first senior appearance for the club came in September 2004 when he scored in a 7-1 League Cup win over Barnsley.