The wing-back system was ripped up, while Pompey unveiled their seventh left-back of the season.
Kenny Jackett’s desire to put Dion Donohue through a midfield test at Rotherham provided plenty to mull over.
We wanted to try to get Donohue into midfield and changed the formation to see if we could go back to what we know and be as strong as we possibly could.Kenny Jackett
And with Sylvain Deslandes handed a Blues debut in Saturday’s New York Stadium encounter in the process, Pompey’s boss has learnt a little more about his squad.
Jackett opted for two changes to the team which drew 1-1 against Scunthorpe, with Oli Hawkins and Connor Ronan dropped to the bench against the Millers.
There was a recall for Matty Kennedy, while the restoration of the 4-2-3-1 system saw Donohue handed a central-midfield start for the first time in his Fratton Park career.
Deslandes completed the changes, replacing Donohue at left-back, and featured for 66 minutes.
A stoppage-time winner from Joe Mattock ultimately handed Rotherham victory, but Jackett was satisfied with his changes.
He said: ‘Sylvain has been here a few weeks and it also gave us a chance to have a look at Donohue in midfield.
‘Sylvain did well, he tired slightly in the second half. It was his first game and we understand that.
‘He’s a good young player and has the power to play in this division.
‘We wanted to try to get Donohue into midfield and changed the formation to see if we could go back to what we know and be as strong as we possibly could, getting some combinations over the pitch with Brett Pitman and Kal Naismith up front.
‘Generally we have got quite a small squad and at times you get injuries – it is no different to a lot of teams.
‘You then need a few players who can play some different positions, you do need two or three.
‘Dion can play central midfield or he can play left-back, they are his positions. At the right time we have to see him in either.
‘I have been pleased with what he has done so far in his Portsmouth career in either position, he is a good player.
‘You need some players that can be variable in one or two positions – and Dion can do that.’
A magnificent defensive performance appeared to have done enough to earn a goalless draw.
That was until substitute Michael Smith crossed from the right for another ex-Pompey player Mattock to head home at far post in the first minute of stoppage-time.
Jackett added: ‘It looked like we couldn’t get out at times, couldn’t get our foot on the ball, couldn’t win the first header up front necessarily where Semi Ajayi was very, very strong – and that was frustrating.
‘But it looked like we had weathered the storm in that particular period, then obviously the late goal has cost us.
‘We had the better chances in the first half, it did look like there were gaps which we didn’t necessarily exploit, with probably two good situations in the second half.
‘Then there was a frustrating passage. From our goal kick going out and it has been played some 45-50 seconds before they (Rotherham) are heading the ball in from four yards out at the back post.
‘Rotherham got their noses in front and it was too late to get back.’