And Pompey's Dejan Stefanovic warned Saints: 'We really mean business this time.'
The Blues stopper is already dreaming of relegating Harry Redknapp's side on Sunday, April 24.
Pompey might have clashes with the likes of Manchester United, Arsenal, Newcastle and Liverpool to come before Redknapp returns to Fratton Park with his new team.
But Pompey's fans, and, it seems, their players, are already looking beyond the Blues' next seven games – when the small matter of their own bid to secure the points that will keep them up should be successfully completed – and to that Sunday lunchtime encounter with their deadliest rivals.
Stefanovic has earmarked the Fratton Park clash as Pompey's biggest game of the season.
The Serb is still furious about the way Pompey lost to a controversial injury-time penalty in the fourth round of the FA Cup at St Mary's last month.
That was Pompey's fourth taste of defeat at Saints in 14 months.
Now Stefanovic is hungry to help Pompey take the perfect revenge by securing a repeat of last season's win over their rivals at Fratton Park.
Stefanovic said: 'Maybe we can send Southampton down in the April game at Fratton Park.
'I think this is the main game of the season now to decide who stays up and who goes down.
'The first priority is for us to stay in the Premiership.
'Then I'll be extra happy for us to relegate Southampton when they come to Fratton Park.
'In our visits to St Mary's we've lost games to late goals and suffered controversial decisions for penalties and sendings-off.
'But from what I saw from our players after the game at St Mary's, we're going to be giving more than 100 per cent when they visit us.
'It's going to be like a war for Southampton when they come here.'
The atmosphere was spicy enough at Pompey when a Yakubu Ayegbeni goal sunk Saints last March.
But Redknapp's departure to St Mary's promises to take the intensity of the derby on to another level again.