Pompey endured a disastrous 20-minute spell to fall to a heavy defeat against Leyton Orient at Fratton Park.
After a positive opening, they fell behind to first half goals from Shaq Forde and, in rather fortuitous fashion, Jordan Brown.
Hopes of a comeback were then ignited – and quickly snuffed out – by a Colby Bishop penalty that was saved.
And Orient soon made the most of that bonus as Dan Agyei struck to effectively end the contest by the interval.
John Mousinho made one change from the side that were beaten at Cheltenham the previous weekend.
Christian Saydee returned to the starting line-up, with Gavin Whyte dropping to the bench, where he was joined by the returning Matt Macey.
Pompey started brightly and were playing at a high tempo, with their opponents struggling to keep hold of the ball.
A couple of long Marlon Pack throws caused problems and the first of them was met by Abu Kamara, whose header looped narrowly over.
The second found Conor Shaughnessy free inside the box, but his attempt was kept out by keeper Sol Brynn.
But Orient began to cause problems of their own as the first half progressed and Forde’s attempt was deflected just over.
Paddy Lane soon had an opportunity at the other end, but his first shot was blocked and the follow-up flew past the post.
Instead it was the visitors who broke the deadlock on 30 minutes, as Forde swapped passes with Max Sanders before slotting home.
And it got worse for the Blues, when Theo Archibald’s corner was not dealt with and the ball flew to Dan Happe.
His shot smacked straight into the backside of team-mate Brown and ricocheted into the net to double the Londoners’ lead.
Pompey soon had a chance to hit back, though, as Jack Sparkes was needlessly scythed to the turf by Forde inside the area.
Referee Benjamin Speedie pointed to the spot, but Brynn guessed correctly to keep out the penalty from Bishop.
The striker had a chance to make amends when he met Lane’s delivery and sent a glancing header agonisingly wide.
And Orient rubbed salt into the wound just before break, as Agyei rose highest to convert another Archibald corner.
Half Time: Pompey 0 Leyton Orient 3
Mousinho made a double change at the start of the second half, with Tom Lowery and Terry Devlin on for Saydee and Sparkes.
It was an attacking switch, with Lane and Kamara being utilised as a makeshift wing-backs in an attempt to find a way back into the contest.
Lowery was soon making an impact and after doing brilliantly to keep the ball in play, he picked out Pack to have a shot that was blocked.
But it quickly came back for the midfielder, who crossed for Sean Raggett to send in a looping header that Brynn caught just underneath the bar.
And Lowery then threaded a fine pass through to Kamara, who was denied by a well-timed challenge in the box by Happe.
But although they kept plugging away and looking to attack, Pompey were struggling to make any real inroads.
Shaughnessy did nod narrowly over from a Kamara cross, shortly before Lane made way for Josh Martin.
Orient had, unsurprisingly, not been quite so adventurous since the restart, although a fierce low shot from Archibald was saved low down by Will Norris.
And with the Fratton faithful heading for the exits, the closing stages petered out without much incident.
Pompey (4-2-3-1): Norris; Rafferty, Raggett, Shaughnessy, Sparkes (Lowery 46); Pack (c), Morrell; Kamara, Saydee (Devlin 46), Lane (Martin 77); Bishop
Booked: Rafferty
Subs not used: Macey, Towler, Whyte, Scully
Leyton Orient (4-2-3-1): Brynn; Galbraith (Turns 79), Beckles (c), Happe, James; Sanders (Pratley 58), Brown; Forde (Pigott 79), El Mizouni, Archibald; Agyei (Sotiriou 62)
Goals: Forde 30, Brown 35, Agyei 45+5
Booked: Galbraith, Pigott, Pratley, Brown
Subs not used: Byrne, Sweeney, Moncur
Referee: Benjamin Speedie
Attendance: 19,477 (1,197 away fans)