Kenny Jackett feels his men enter the meeting with Rovers as outsiders, despite their impressive home form this season.
Only two sides in League One have won more games than the Blues on their own patch this term.
They face a stern test of their credentials, however, as they welcome the promotion-chasers to Fratton Park.
Jackett knows the size of the task which lies in wait for him team tomorrow night.
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He said: ‘I have a lot of respect for them and their manager.
‘They are one of the best clubs and squads in the league.
‘We’re not stupid. We know how strong they are and the strengths they have.
‘I think we go into the game as underdogs.
‘Our fans will thrive on that, because there’s no doubt we will need to be at our best to beat Blackburn.
‘We’ve got a strong home record, though, and a very good crowd to bring into play when we can.’
Jackett remembers the frustration and disappointment felt as the Blues were well beaten 3-0 at Ewood Park in October.
It’s one of the rare occasions this season when a gulf in quality between Pompey and their opponents has been evident.
Putting that poor result right will be a motivation for the team, as they look to reel in the play-off-chasing sides above them in the table.
Jackett added: ‘When we went to Blackburn the first goal came after 37 minutes and it was a good goal by Bradley Dack. Clinical.
‘From then on the more we went forward and the harder we tried, the more they looked like scoring.
‘It ended up 3-0 and we can’t complain about that particular result.
‘They were good on the day and deserved to win.
‘We want to try to get one back if we can.
‘On any one day it can be turned over. That’s the beauty of football.
‘Home advantage is a big thing and our record is strong.
‘It’s another game with a fair few months in between since our last meeting.
‘We understand the opposition are strong, but we don’t spend too long concentrating on them.
‘We want to focus on ourselves and make sure we take the chance in our attitude and body language.
‘We have to recognise the opportunity we have because there’s a big one there now.’
- JORDAN CROSS