Andre Brooks scored a 90th-minute winner to give Sheffield United their first away victory in six games and keep their hopes of a play-off place alive with a 1-0 success at Portsmouth.
The last-gasp triumph leaves Chris Wilder's side six points off the top six whilst Pompey are just a point above the relegation zone.
United's on-loan Manchester City midfielder Kalvin Phillips started his first game since March last year as Pompey dominated the first half, with the home side left to rue a string of missed opportunities.
The first chance of note went the way of Pompey after Millenic Alli cut in from the left and scooped over a cross which Ebou Adams headed narrowly over.
Gus Hamer is yet to discover the form he showed last season but he was prominent down United's left and struck the base of a post after driving along the by-line.
It was John Mousinho's Pompey enjoying most of the early pressure with Alli causing plenty of problems for United right-back Femi Seriki.
Another of his runs saw the ball fall to John Swift in the six-yard box but he was denied by the feet of Michael Cooper before the loose ball was cleared.
Soon afterwards Alli had a chance of his own after Seriki's slip but Cooper saved his low shot comfortably. Pompey thought they had scored through Colby Bishop but James Linington had blown for a foul in the build-up.
Wilder did not see his men manage a single shot on target during the first half, with Patrick Bamford's looping header onto the roof of the net one of the only efforts at goal for the Blades.
Wilder made a change at half-time, bringing on Callum O'Hare for the ineffective Tom Cannon but again, it was Pompey who were dominant.
Next to go close was Swift, who curled an effort agonisingly beyond the angle of post and crossbar after a well-worked corner from Adrian Segecic.
There had been little for the 1,375 travelling supporters to cheer but the Blades began to impose themselves on the game.
Hamer was starting to find a little more space on the left and drove inside to shoot just beyond the far post from 25 yards as the Blades built more momentum.
The chances kept coming. First, Bamford saw a header saved by Nicolas Schmid and then Brooks just missed the top corner with a shot from the edge of the area.
In the last minute, substitute Tyrese Campbell drove down the left and pulled the ball across the six-yard box where Brooks was waiting to slide the ball home and give United the points.
Portsmouth's John Mousinho:
"I thought the first half we were really dominant, very good performance, but we didn't show enough composure in front of goal and slashed at a couple of opportunities.
"It was a slightly different game in the second half, but I thought once we got to grips with it, we looked more likely to win in the last 20, 25 minutes and unfortunately got caught on the break.
"Every game from now until the end of the season is going to be massive. The next one is the biggest one."
Sheffield United's Chris Wilder:
"Sometimes games are won on mentality. You can't always play well. We played well on Monday against arguably the best team in the division (Middlesbrough).
"The art of what you need to do is when you're not at your best, which we weren't, is that you have to rely on your mentality. If we weren't together, then we'd have been rolled over.
"It's the next game. You win games of football, you go up the division. If we were 24th, I'd want to be 23rd. If we were 10th, I'd want to be ninth. And if we were top, I'd want to be top by 10 points. So that's our attitude. We're not top."
