Christian Burgess insists Pompey’s recent defeat of Northampton Town in the Checkatrade Trophy counts for nothing ahead of Saturday’s clash.
The League One showdown at Fratton Park will be the third time the two teams have met this season.
It was the Cobblers who earned the three points in the reverse league fixture in September with a 3-1 victory.
But the Blues delivered a comprehensive 2-0 success against Jimmy Floyd Hasselbaink’s troops in the Checkatrade Trophy second round at Fratton Park earlier this month.
Although Burgess believes Northampton were ruthless at Sixfields, he reckons defensive lapses also cost Kenny Jackett’s outfit.
Meanwhile, the centre-back insists tomorrow’s League One fixture will be completely different to the cup battle.
Burgess said: ‘You can’t read too much into that win with it being that competition.
‘Players sometimes go out there with completely different mindsets so it will be a completely different game on Saturday.
‘In the first game they were very ruthless. The first goal they scored, they took it very well and put us under pressure.
‘But we’d probably blame ourselves more for the goals we conceded.
‘They did go on a little bit of a run when they first got their new manager but have since dropped off so we’ll be hoping to be ruthless, to apply pressure and get the crowd going.
‘We’ve been really strong at Fratton so it’s in our best interest to keep that going.’