The 23-year-old was part of the Shrimpers squad who dropped out of the Football League last season.
He spent the second half of the campaign with the Roots Hall outfit on loan from the Blues.
Hackett-Fairchild had a brief spell with former club Bromley in the first half of last term before his January move to Southend as he searched for much-needed game time.
The minutes the forward craved did come with Mark Molesley’s men as he racked up 25 appearances for the club.
But being part of a struggling side who eventually sacked Molesley before their relegation from League Two was confirmed, Hackett-Fairchild failed to have the goal impact he desired, netting just once.
Hackett-Fairchild told The News: ‘Obviously, it’s never good when you get relegated. It was tough.
‘It was the first time I’ve been in a team who haven’t been in the top half of the table so it was a massive learning experience and I take a lot from it.
‘I feel like it’s made me grow a lot as a player.
‘Football-wise, I didn’t get the goal return, I didn’t get enough assists. But it was good for me to be in a team that isn’t doing well because it’s a different type of mentality and it adds to my game.’
Hackett-Fairchild is now back at Pompey with a point to prove to head coach Danny Cowley.
Since moving to the Blues in January 2020, he has managed just one EFL Trophy appearance for the club.
But he did find the net in Pompey’s 5-2 pre-season friendly triumph over the Hawks at Westleigh Park on Saturday, after coming on at half-time.
And Hackett-Fairchild is keen to put himself in Cowley's thinking this pre-season and end the campaign as a League One promotion winner at Fratton Park.
He said: ‘Obviously, the end goal is to get promoted, that’s what we’re focusing on as a team, that’s the main most important thing. We need to get promoted.
‘You’ve got to keep your body in a good condition to come back and start sharp so that’s what I’ve tried to do and tried my best.’