It was a half-time tactical substitution vindicated in stoppage time.
And Kenny Jackett was delighted with the impact of Stadium MK matchwinner Conor Chaplin during a rare first-team outing.
With Conor, quite frankly we haven’t scored enough goals, so it’s finding a way to get him in on a regular basisKenny Jackett
The 20-year-old had not been utilised from the bench in Pompey’s previous four matches.
But he was introduced at the interval alongside Jamal Lowe in a double substitution for Matty Kennedy and Connor Ronan.
The Blues had been trailing to MK Dons’ Ike Ugbo’s 21st minute opener – but drew level on 84 minutes through Matt Clarke’s header.
Then, four minutes into time added on, Chaplin pounced with a left-foot finish for a dramatic finale.
Jackett explained: ‘I felt Conor could support Brett (Pitman) a little bit more than we had done in the first half.
‘While we had a lot of the ball in and around their box, I didn’t see where the goals were really coming from in that period. MK Dons were sitting deep around their box and it was very tough for us to break them down.
‘There were shots around the box, but we didn’t do enough.
‘In addition to a second forward getting closer to Pitman, I felt that, particularly on the break, Lowe’s pace could have an impact.
‘I wanted us to get him into the many holes that were there because they play an expansive game. It does create, but similarly leaves them open at the back and it can be cat and mouse.
‘With Conor, quite frankly we haven’t scored enough goals, so it’s finding a way to get him in on a regular basis, which is what he wants.
‘He’s 20, has just ticked over 100 games, although a high amount of those are from the subs bench.
‘He had a good crack at it on Saturday, 45 minutes in total, which was what I felt was needed in the second half.’
In an open match, both keepers impressed, particularly man-of-the-match Luke McGee on his first-team return.
Oli Hawkins struck the post and Brett Pitman had one cleared off the line during the second half, but finally Pompey got the win.
Jackett added: ‘There were a lot of chances at either end.
‘We dominated the first 20-30 minutes, but they scored against the run of play when we were on top – and that gave them some confidence.
‘I felt the game could have gone either way, both sides went for it.
‘It breaks a tough run of results through January and should give the players a lot of confidence to build on, knowing they can come back in those circumstances.’
– NEIL ALLEN