Izale McLeod snatched a last-gasp point to finally end Pompey’s losing streak in a 1-1 draw at Coventry.
The Blues were heading for what appeared to be a deserved 1-0 defeat.
Gary McSheffrey netted in the 41st minute, having picked up a pass through the heart of the Blues’ defence.
The hosts also struck the post through William Edjenguele and, later, Carl Baker during a dominant display.
Pompey, who mustered just one goal attempt in the first half, were comfortably better after the break.
Yet with the match well into five minutes of time added on, substitute Adam Webster knocked a long ball into the box and McLeod ghosted in on the far side to poke the ball home.
In truth, had it not been for debutant Alex Cisak, Coventry would have been well out of sight at that stage.
As it is, the result ends a run of seven successive defeats for Pompey and provides a crucial confidence boost for Guy Whittingham’s men going into a two-week period before their next fixture.
Whittingham named Ricardo Rocha in the starting line-up, while Johnny Ertl received a recall and Cisak featured.
Nathaniel Mendez-Laing and Gabor Gyepes made way – as did the departed Mikkel Andersen - in three changes to the side which lost to Leyton Orient in the week.
When the match got under way there was a nervy start from Cisak on nine minutes when Cyrus Christie got forward to swing in a cross from the right.
The on-loan keeper failed to hold the Coventry full-back’s centre but fortunately there was nobody around to capitalise and Lubomir Michalik had time to clear.
In the 14th minute the Oldham stopper pulled off a good save, palming Carl Barker’s deflected shot from inside the box wide.
Moments later, Cisak came to Pompey’s rescue with a stunning relax stop to thwart the hosts after Gary McSheffrey’s free-kick appeared to be destined for the far corner.
The visitors remained under the cosh and William Edjenguele’s header from a right-wing corner was blocked by Ertl on the line and cleared.
Pompey had their first attempt on goal in the 34th minute when Izale McLeod surged down the left and cut inside before firing a shot into the side netting.
Yet in the 41st minute Coventry broke the deadlock when a ball down the middle put McSheffrey through and he calmly slotted it past Cisak.
Pompey started off bright after the interval but Cisak again had to be relied on when Rocha produced a poor clearance in the 51st minute.
The ball came to David McGoldrick, who was played on-side by Howard, and the strike drove in a low shot which was diverted over the by the Blues keeper.
From Baker’s resulting corner, Edjenguele’s far-post header struck the post and was hacked off the line with the defender appealing it had crossed.
At the other end, in the 78th minute Darel Russell drew a good save from Joe Murphy with an angled drive.
In the 88th minute Baker almost doubled scoreline when his shot from distance struck the bar and McGoldrick’s follow-up was ruled offside.
However, there was a further twist when McLeod popped up at the far post to snatch a dramatic point of the visitors.
COVENTRY 1 (McSheffrey 41)
POMPEY 1 (McLeod 90+3)
Coventry: Murphy, Baker, McSheffrey, Jennings, Christie, Wood, Edjenguele, McGoldrick, Moussa, Bailey, Adams. Subs: Dunn, Clarke, Cameron, McDonald, Fleck, Barton, O’Donovan.
Pompey: Cisak, Dumbuya, Michalik, Rocha, Harley, Ertl, Russell, Howard, Allan, Benson, McLeod. Subs: Eastwood, Walker, Gyepes, Jervis, Harris, Webster, Mendez-Laing.