BILLY Sharp scored twice to send his former club spiralling closer to the Championship trap door.
Sharp was making a rare start for the Saints after a stuttering introduction to life on the south coast.
But he did not waste the opportunity to fire his new side another step closer to the Premier League - and condemn his former club to another defeat.
Doncaster Rovers are looking in the other direction to Southampton and will be upset at the defending that allowed Sharp to steal the show.
He was allowed to get in between defenders and head home a 58th minute corner from point blank range to settle the nerves at St Mary's.
Sharp then rubbed salt in Doncaster's wounds with 15 minutes remaining when he brushed aside Habib Beye and fired past an exposed Carl Ikeme to settle the game.
Rovers were organised in defence and also a threat in attack during the first half, and could easily have gone in ahead at the break.
Freddie Piquionne headed a good chance wide and El Hadji Diouf wasted a glorious opportunity when his shot was blocked with the goal at his mercy.
Rovers had no answer to the Saints and Sharp after the break, however, and are running out of time in the battle to beat the drop.
This season is fast turning into a tale of ifs, buts and maybes.
Rovers fans were tonight left wondering if they would be in the same position had Billy Sharp not swapped Rovers' red and white hoops for the stripes of Southampton.