Pompey will need every available member of their squad firing during a gruelling run of games.
Tuesday evening’s clash with Blackburn at Fratton is the second of five fixtures in the space of just 15 days.
With a number of players still on the sidelines, it is a relief to have defender Christian Burgess back from suspension against Rovers.
And Jackett wants his troops to make the most of the large number of points that are up for grabs.
The Blues boss said: “It’s a big run of games coming up and that gives us an opportunity to show we’re one of the better sides in this division.
“Season-defining is a good way of putting it and it’s encouraging that we find ourselves in this position at this stage of the year, instead of at the wrong end or out of the race.
“There are a lot of points available to us in a short space of time and we’re chasing those top clubs.
"Season-defining is a good way of putting it and it’s encouraging that we find ourselves in this position."
“We’ve made the transition to League One quite quickly, but you aspire to be successful and we’re firmly in the hunt.
“But we’re looking at a group of players rather than just 11, especially with Southend to come on Saturday and then Fleetwood the following Tuesday.
“You need to be ready to make changes if that’s required, perhaps because of injuries and suspensions.
“So the more good players you have available – and I include Burgess in that – the better is it for everyone.”
Pompey will face a Rovers side who are sitting a single point outside of the automatic promotion places.
Jackett said; “I have a lot of respect for Blackburn and the players – and management team – that they have.
“We know their strengths, but the main thing is making sure we set our own standards and keep improving.
“We’ll be slight underdogs and that can suit us. We want a performance that gets our crowd going and we’re certainly capable of that.”
Conor Chaplin came off the bench to grab a dramatic late winner at MK Dons on Saturday, having not featured in the league since the end of December.
Jackett said: “I want him to be a main player at Pompey, but he’s only just coming up to his 21st birthday.
“He’s one of the many good young footballers we have at this club and I see a future for him here – not anywhere else.
“Starting games is what he’s aspiring to do and he already has more than 100 appearances for the club.
“It’s quite right that he’ll want more minutes from the beginning and his performance on Saturday will only encourage me to give him that.”