It was a surprise half-time switch from Paul Cook’s trusted Pompey system.
Yet Leam Richardson credits the arrival of the 3-5-2 formation against Barnet for lifting the Blues into third spot.
Pompey headed in at the break 1-1 on Saturday after Conor Chaplin had cancelled out Andy Yiadom’s opener.
The second period would see Adam McGurk and Chaplin both net to clinch a 3-1 success, while Bees keeper Jamie Stephens was dismissed in the 66th minute.
Having endured an unimpressive opening 45 minutes, the favoured 4-2-3-1 was ditched to inspire a Blues side robbed of the injured Gary Roberts at the break.
And the outcome delighted Pompey’s assistant manager.
Richardson said: ‘We did what we thought was right at the time and with Gary coming off it disrupted the balance of the team a little bit.
‘But we felt we could penetrate a lot more at the top-end of the pitch, we wanted to play a little bit quicker, we need to be a bit more dynamic and thankfully it worked.
‘To be fair, Adam Webster has been screaming to play, the gaffer can see a right good player in the tools he has got and with him, Christian (Burgess) and (Matt) Clarke we have a lot of balance and doesn’t veer a lot from where we want to be.
‘It just gets us up the pitch quicker and gets us more productive in a certain area, especially when teams come to try to stop you playing.
‘It’s our job to always think and try to be productive in what we do. Sometimes it will work and sometimes we will get our rewards, thankfully we did that Saturday.
‘The performance overall was okay, I think the result will mask where we want to be – with the greatest of respect to the players.
‘There is still a lot of work to be done but we are in a good place at the minute so we will continue to try to be repetitive on our lads with the habits and the work ethic and what we expect from them.’
The role of Darren England in the result was also a talking point among those present, particularly his second-half display.
Barnet head coach Martin Allen criticised the South Yorkshire official’s decision to allow McGurk’s goal after Kyle Bennett had been flagged for offside.
Then came a second yellow card for keeper Stephens following a foul on Bennett, having been booked earlier for time wasting on 30 minutes.
Richardson added: ‘The officials have a tough job and I think players now have a tough job because the game is that fast.
‘Is he interfering? Isn’t he interfering? They will argue they have stepped up because he was there and he was interfering because their lines changed, it’s a tough one.
‘With the rules I’m sure it’s not offside, but in the great scheme of things it’s an on-going debate.
‘Football is trying to make the game better, they are trying to make it faster for the fans to come and watch and get their money’s worth and get their entertainment. Let’s hope it doesn’t happen to us!
‘But Bennett was not interfering, Barnet were playing the high line all day to try to squeeze the game and try to be productive in their shape.’