It looked as though Pompey’s quest for automatic promotion was about to suffer a setback at Burton.
A fine strike from Ben Close had given them the lead, only for Liam Boyce to level just after the interval.
But there was an almighty goalmouth scramble in the Brewers box deep into stoppage-time and Matt Clarke popped up to score the winner.
It sparked jubilant scenes in the away end and Kenny Jackett was delighted with a result that ensures his side’s fate is still in their own hands.
The Blues boss said: “When I saw the ball land for Matt’s left foot, I was optimistic and he didn’t need asking twice to slot it home.
“It was a great moment for him right in front of our fans, who cheered us on throughout a difficult game.
"At the moment it’s nip and tuck, but I’m pleased to say that we’re still very much in there with four matches to go."
“The win keeps us right in the hunt and it’s important that we maintain that pressure on second spot.
“At the moment it’s nip and tuck, but I’m pleased to say that we’re still very much in there with four matches to go.
“Congratulations to the players because we’ve got 83 points now, which is excellent, and our away record is up there with anyone in all four divisions.
“There’s not much between any of the teams up there, so we have to keep fighting and keep believing.”
Jackett had to make changes after the break, as the hosts began to take control of the Pirelli Stadium contest.
He said: “We showed a resilience that was needed because although we took the lead, Burton came out for the second half and dominated.
“They deserved to get back into the game and then from 60 minutes onwards, it really could have gone either way.
“We brought Bryn Morris on to give us that extra midfielder when we needed it and had the mobility of Omar Bogle.
“Ronan Curtis also came on to make a difference and we managed to turn the tide, working hard to get the winner at the end.”