Wes Thomas has urged his Oxford United team-mates to take advantage of Pompey’s uninspiring home results.
The Blues have taken just two points at Fratton Park in 2018 – compared to nine on their travels.
Kenny Jackett’s men actually headed into the turn of the year on the back of six-successive victories on home soil.
Yet the tide has turned, with disappointing Pompey booed off in the past two Fratton fixtures, both ending in defeat.
On Sunday, the U’s venture to the south-coast in League One with new boss Karl Robinson at the helm.
For Thomas, it will be a return to the club were he scored three times in seven loan appearances under Michael Appleton in 2012-13.
And he’s hoping Oxford can capitalise on the hosts’ present lean spell.
He told the Oxford Times: ‘When I was there they were a really decent crowd.
‘I don’t think I’ve been there when they’ve got on the players’ backs or anything. They have always been really supportive.
‘They will probably be a 12th man for them, but the home form hasn’t been great and there will probably be a few nerves for their players.
‘Hopefully, we can take advantage of that.’
Following Pep Clotet’s sacking in January, assistant head coach Derek Fazackerley had stepped up to serve as caretaker.
His eight-game spell yielded only two wins, although they defeated Peterborough 2-1 last weekend.
It leaves the U’s currently in 16th place – a disappointing position having finished within three points of the play-offs last season.
Yet, in recent times, Fratton Park has proven a profitable visit for the club, with Oxford undefeated since the 1997-98 campaign.
The most notable visiting triumph was in the opening match of the 2013-14 season, when a Pompey under fan ownership and Guy Whittingham suffered a 4-1 reverse.
Fazackerley added: ‘The result against Peterborough was pleasing for everyone because we have come under a little bit of pressure, certainly in the home games.
‘We’re going to Portsmouth in a game that’s on TV. There will be a massive audience, hopefully, and it’s a place we’ve done well.
‘Hopefully, there will be a good atmosphere, a 16-17,000 crowd, and it’s a great place to play.
‘I think Portsmouth, like us, have suffered a little bit at home recently and the pressure’s on them.’