Pompey were pushed down into second spot in the League One standings on Saturday.
While they were drawing with QPR in the FA Cup, Luton took advantage by beating Southend to climb into first position.
The sides could swap again on Tuesday evening, with the Blues travelling to Kenilworth Road in a mouth-watering contest.
And while Joe Gallen hopes they can inflict a first home league defeat of the season on the Hatters, he knows that this result will not decide anything.
Pompey’s assistant manager said: “We’ve been top for so long and I didn’t quite know what that meant because it’s where you are on May 4 that really counts.
“I think the people at this club understand that because of what happened here just a couple of years ago.
"The players, manager and supporters have all been fantastic and we’ve got big game after big game, which is what we’re all here for."
“There’s no pressure – we’re just excited. We get this one out the way, then we play Doncaster, then the replay. I like the fact that we’re all in this together and we’ll see where it ends up.
“A lot of confidence was flying around the dressing room after the QPR game and we want to take that into these league fixtures.
“We’re very excited about the rest of the season and to still be involved in three competitions is very good going.
“The players, manager and supporters have all been fantastic and we’ve got big game after big game, which is what we’re all here for.”
Pompey’s opponents have enjoyed a run of 16 successive matches unbeaten in the league to propel themselves up the standings.
Gallen said: “Luton have got a very good system that’s they’ve had for a long time now. They’ve been well coached and have got recruitment right.
“It’s a club on the up and they’re playing some nice football at the moment, but we’re in a decent position ourselves.
“We’ll have a big job on our hands because no team has gone there this season and come away with three points.”
Gallen revealed that Oli Hawkins and Nathan Thompson are both close to returning for Pompey after spells out injured.
He said: “They have both trained and they’re very close. We’ll probably leave them for Luton and they should be ready for Saturday.”