The Division Two encounter was due to kick-off at 3pm (GMT) on Friday, 5th November but will now begin at 12pm, taking place at the Saints' Staplewood Training Ground.
The young Magpies currently sit in seventh place on 13 points, one adrift of the play-off spots, while Southampton - who suffered relegation from Division One last term - occupy 13th with eight points.
The two sides last met in the Premier League 2 Division Two play-off final in May 2019, with the Hampshire outfit claiming a 2-1 win over United's second-string at St. Mary's Stadium.