Hayden Mullins believes fortress Fratton can see off the high-flying Hammers.
Pompey are unbeaten on home soil since losing to Peterborough in September.
And while West Ham have the best away record in the Championship, Mullins knows the Blues can be more than a match for his old side tomorrow.
The 32-year-old said: ‘I think we have some solid league form at the moment. At home, we have got a much better record than we do away from home.
‘Our home form is probably up there with the best in the division – in the top five. We feel really confident and will give anyone a game.
‘Our away form is the thing that’s letting us down this season and we all know that.’
West Ham are level on points at the top of the Championship with Southampton – and Mullins has backed them to return to the Premier League at the first attempt.
The midfielder, who spent six years at Upton Park and helped them win promotion in 2004-05, said: ‘I think you’ve got to look at them and admit that their squad is really good and they should definitely be up there in the top two at the end of the season.
‘They have got a very good squad and we know all about them. They’ve got a lot of depth and can shuffle their pack.
‘They’ve got good strikers, good midfielders and it’s a Premier League squad, really.
‘They are up there on merit and we know what a tough game it will be.’
After his rare strike in the 2-0 win over Watford in Pompey’s last home game, Mullins is pessimistic he’ll be celebrating again.
He smiled: ‘I don’t know if I’ll score another one now until next year!’