Pompey’s promotion charge received a set-back as they collapsed to defeat at Stevenage.
Despite hitting the woodwork twice, goals from Jack King and Matt Godden meant they deservedly trailed at the break.
Jobi McAnuff then wrapped things up in the opening seconds of the second half, while a red card for Christian Burgess and missed Conor Chaplin penalty served to perfectly sum up the Blues’ afternoon.
Paul Cook made two enforced changes from the side that beat Grimsby on home soil earlier in the week.
Kyle Bennett and Kal Naismith both went off injured against the Mariners, so in came Tom Davies and Noel Hunt in a switch to a 3-5-2 system.
The visitors won an early corner and Carl Baker’s delivery was headed clear, with Davies receiving a bloody nose that forced him to change into a numberless shirt.
Enda Stevens then cut the ball across the face of goal and Gareth Evans charged in to send a fierce shot thudding against the crossbar.
But it was the hosts who then started to take control and they almost broke the deadlock on 12 minutes.
David Forde dived to his right to palm clear Steven Schumacher’s well-struck free-kick and then keep out Josh McQuoid’s follow-up.
The ball again fell to McQuoid, though, and his effort had to be hacked from the line by Matt Clarke, with referee Michael Salisbury ignoring pleas from the home fans that it had crossed.
But it was only a brief respite for the Blues and when an ambitious attempt from former Fratton trainee Luke Wilkinson cannoned back off the crossbar, the ball fell kindly for King to nod home.
Pompey tried to hit back and when Stevens’ cut-back evaded both Baker and Eoin Doyle, a shot from Evans flew wildly out of the ground.
Boro were looking full of vigour, however, and after Tom Pett surged through the centre, his strike had to be saved by Forde.
And they did double their advantage on 28 minutes when McAnuff found Godden in acres of space at the back post to fire into the net.
That finally seemed to spark Pompey into life and they did finish the first half strongly, without being able to find a goal.
Baker went closest with a fine free-kick that struck the underside of the bar and hit Stevenage keeper Chris Day, only to ricochet to safety.
Another Baker set-piece on 37 minutes then just evaded the leaping Davies and landed safely into Day’s arms.
Pompey would have wanted to build on that positive play just before the interval, but instead found themselves further behind within seconds of the restart.
Godden took advantage of some dithering defending to barge into a shooting position and although Forde did well to deny him, the keeper was powerless to prevent McAnuff from converting the loose ball.
The Blues tried desperately to find a route back into the contest, although their hurried play led to some sloppy moments.
They had a chance to reduce the deficit when Baker’s corner hit a defender in a crowded box and flew narrowly past the post.
But Stevenage were still looking a real threat on the counter-attack and when McAnuff picked out Godden, Davies had to get a block in.
Cook made a double substitution on 64 minutes, with Nicke Kabamba – making his senior debut – and Gary Roberts replacing Hunt and Baker.
A low delivery by Stevens then had to be cut out before it leave the lurking Eoin Doyle with a simple tap-in.
Chaplin came on for Eoin Doyle as Cook made his final throw of the dice, but the afternoon soon got worse for the Blues.
Burgess was booked for a foul and having already been carded for an earlier indiscretion, he received his marching orders.
But there was still time for more misfortune to befall Pompey as they missed an excellent opportunity to grab a consolation.
A penalty was awarded when Fraser Franks tripped Chaplin in the box, but the substitute hit his penalty down the middle and straight into Day’s arms.
That failed to dampen the noise emanating from the away end, though, as the Pompey fans kept cheering on their side despite a disappointing display.
Stevenage (4-2-3-1): Day; Franks, Wilkinson, King (c), Ntlhe (Gorman 74); Pett, Lee; McQuoid (Hinds 67), Schumacher, McAnuff (Loft 88); Godden
Goals: King 16, Godden 28, McAnuff 46
Booked: Wilkinson, Pett, Gorman, Franks
Subs not used: Preston, Johnson, Tonge, McKee
Pompey (3-5-2): Forde; T.Davies, Burgess, Clarke; Evans, Baker (Roberts 64), M.Doyle (c), Rose, Stevens; Hunt (Kabamba 64), E.Doyle (Chaplin 73)
Sent off: Burgess (two yellow cards)
Booked: Stevens, Baker
Subs not used: O’Brien, Talbot, Linganzi, Lowe
Referee: Michael Salisbury
Attendance: 4,185 (1,390 Pompey fans)