The Blues will face off against Sunderland tonight with everything riding on the two-legged showdown with their familiar rivals.
Jackett feels those circumstances mean the season has now entered cup territory.
His team have shown they can handle that kind of cut-throat territory with a march to the fourth round of the FA Cup followed by Checkatrade Trophy victory.
Jackett is hopeful the attributes Pompey have exhibited previously in such terrain will again come to the fore.
He said: ‘It’s 100 per cent a cup competition.
‘It’s 180 minutes and it does change, definitely.
‘We have been reasonably successful in the cup competitions so hopefully we can continue to be.
‘In terms of your team selection you have to be slightly different, more wide-ranging for the league.
‘For the players as well, they have to know and recognise that in the first leg obviously there is a second leg coming.’
Jackett is also out to continue a strong record in play-off semi-finals in his managerial coaching career.
The Pompey boss has won four times at this stage of the competition with Millwall, Swansea and as a coach with QPR.
That contrasts with the Blues’ two play-off semi-final since their inception in 1987.
Jackett added: ‘When I was at Swansea we lost on penalties to Barnsley.
‘Semi-finals have been good, the final so-so.
‘People tell me Pompey have never won a play-off game. These stats are meant to be broken so perseverance, keep going, it will work for us.
‘You look forward to it, see it as a chance.
‘One of the clubs will get into the Championship. That's a big carrot and we have to go for it and see if it can be us.
‘You have to make sure mentally, physically and tactically you are at your maximum and are ready.’