Marc McNulty missed a penalty as Pompey fought from behind to claim a point at Mansfield.
It looked bleak for the Blues when, within the space of a few minutes, McNulty saw his spot-kick saved and Matt Green slotted the hosts ahead.
But Ryan Tafazolli’s own-goal levelled the contest before the interval and neither side was able to take any of their second half chances.
Paul Cook made two changes from the side beaten at home by Newport the previous week.
One of them was enforced, with Michael Smith replacing the suspended Gary Roberts, while Gareth Evans dropped to the bench to make way for Kal Naismith.
There was not an abundance of chances in the early stages, although the hosts survived a defensive mix-up early on, while Mitchell Rose was unable to beat Ryan Fulton with an angled drive.
Pompey’s keeper then had to race from his area to clear after a blocked Christian Burgess shot turned into a quick Stags attack.
Set-pieces were causing the most problems for both sides, with Mansfield delivering some dangerous free-kicks and the Blues threatening from corners.
But it was penalty that gave the visitors a golden opportunity to break the deadlock on 20 minutes.
McNulty was brought down in the box by former Pompey loanee Daniel Alfei, but his spot-kick was brilliantly saved by Scott Shearer low to the keeper’s left.
And the Stags soon made him pay for his profligacy by taking the lead themselves, as Emmanuel Dieseruvwe teed-up Green for a cool finish.
Referee Carl Boyeson upset the mood of the home fans, however, by issuing a flurry of yellow cards, not that Dieseruvwe, Rose or Green could have much to complain about.
Pompey, meanwhile, were trying to find a leveller, but despite some neat passing forward, they were doing little to trouble Shearer.
Instead, the keeper was finally beaten by one of his team-mates just before the break, with TAFAZOLLI inadvertently turning a Ben Davies corner into his own net.
Mansfield Town 1
The second half was slow to get going, although it was the Blues were looking the more likely to score again.
But they were limited to a couple of scuffed efforts from Enda Stevens and Smith that did little to trouble Shearer.
Kyle Bennett went closer on 65 minutes when he met Davies’ corner with a volley that was heading for the net before it was deflected wide.
The visitors had a chance of their own when Stevens was booked for a foul on Dieseruvwe, but the resulting free-kick was confidently plucked from the air by Fulton.
Cook soon made his first substitution, with Ben Tollitt replacing Bennett wide on the left to add some youthful exuberance to Pompey’s attack.
And the Blues boss made another switch to his front line moments later, with McNulty making way for Adam McGurk.
The hosts had been growing in confidence as the half progressed and almost retook the lead on 62 minutes.
Fulton had to get down to his right to push clear Rose’s skidding, long-range effort and then denied Green from the resulting corner.
His counterpart Shearer had looked assured in the Stags goal, but almost made a hash of Michael Doyle’s opportunistic strike from distance on 77 minutes.
There was then a break in play when one of the linesmen appeared to injure his arm and had to be replaced – not that he received much sympathy from the stands.
Conor Chaplin was introduced in place of Naismith for the final five minutes, as Pompey went in search of a winner.
But, despite the fourth official announcing six minutes of stoppage-time, neither side was able to snatch victory.
Mansfield (4-4-2): Shearer; Alfei, Pearce, Tafazolli, Benning; Rose (Daniel 86), Collins (c), Clements, Kavanagh (Blair 64); Green (Thomas 83), Dieseruvwe
Goals: Green 26
Booked: Dieseruvwe, Rose, Green
Subs not used: Jensen, Baxendale, Chapman, Beardsley
Pompey (4-2-3-1): Fulton; Davies, Burgess, Webster, Stevens; Hollands, Doyle (c); Naismith (Chaplin 85), McNulty (McGurk 70), Bennett (Tollitt 67); Smith
Goals: Tafazolli 43 (og)
Subs not used: Bass, Clarke, Barton, Evans
Referee: Carl Boyeson
Attendance: 3,980 (1,192 Pompey fans)