Gareth Evans’ opener had been cancelled out and it looked like Pompey would have to hang on for a point.
But late intervention from Ellis Harrison ensured that they actually departed Doncaster with all three in the bag.
The striker – who had been brought on at the start of the second half – deftly guided home James Bolton’s cross in stoppage-time to secure the win.
And he was also pleased with the way that the Blues soaked up pressure from the hosts before doing damage at the other end.
Harrison said: “We had to hold on at times and not many teams will come here and pick up three points.
“I was sat on the bench during the first half, but it was a tough contest and we had a game-plan that was sensible.
"I should have made better contact from an earlier cross from Gaz, but I knew that I’d caught the second one perfectly."
“The manager gave us a boost with his team-talk at half-time and it worked perfectly for us in the end.
“I should have made better contact from an earlier cross from Gaz, but I knew that I’d caught the second one perfectly.
“The keeper had made a great save from Closey’s effort and so I was just hoping that he wouldn’t get a touch on it. Thankfully, it dipped over him.
“It’s an unbelievable feeling to score the winner and secure the three points, although there was still a lot to do after the goal.
“Burgey and the whole defence were getting the blocks in and I had to head one away in the last 10 seconds.
“We had to defend well, but it’s not luck when you’ve got so many people throwing themselves in front of shots.”
Harrison has been a substitute for many of Pompey games so far this term, but you will not find him sulking about that.
He said: “I need to keep doing what I’m doing. If I’m sat on the bench then I have to be ready to come on because the team is more important than me.
“Everyone has to be patient and I was still happy when we beat Bolton the previous week, even though I didn’t get on. The club is bigger than any one player.”