Pompey suffered defeat in their latest encounter with familiar foes Sunderland, despite taking the lead in the north-east.
A first goal for Marcus Harness since his summer switch from Burton broke the deadlock – and the Blues were good value for their lead.
But the Black Cats had turned things around by the interval, with Jordan Willis heading a leveller before Chris Maguire struck against his former club.
There were chances for the visitors to leave with at least a share of the spoils, but Sunderland held on for the win.
Kenny Jackett made one change from the side that beat Tranmere on home soil the previous weekend.
John Marquis returned to the starting line-up to lead the line, with Ellis Harrison dropping to the bench.
Former Blues loanees Marc McNulty and Maguire both featured for the hosts, with the latter having scored the decisive goal in last season’s play-off clash.
It was Pompey who made the brighter start and a cross from Anton Walkes in the opening seconds was diverted over by Ronan Curtis.
Ben Close has netted a couple of recent stunners and tried his luck with another 30-yard effort, although this time the ball narrowly cleared the crossbar.
Then, after Marquis had done well to win a corner on the right, Lee Brown’s delivery was cleverly collected by Jon McLaughlin.
The Sunderland stopper soon had to come racing from his line to stop Marquis latching onto Close’s fine pass.
And the visitors made their dominance count by breaking the deadlock midway through the first half.
Harness played a neat one-two with Marquis and was unable to dig out a shot, with his team-mate also failing to make a clean connection at the second attempt.
But the ball fell for HARNESS and he made no mistake, sweeping home a shot to open his goalscoring account for the club.
The lead did not last long, however, as Willis charged into the box to powerfully convert a Grant Leadbitter corner.
Both sides were looking capable of adding to the scoring as the half progressed, although it was the hosts celebrating on 39 minutes.
Walkes tried to stop Aiden McGeady, but his interception ricocheted against the winger, who continued his charge
The Irishman then played a lovely pass across the face of goal, with Maguire there to slot past a helpless Craig MacGillivray.
The hosts did receive a blow soon after the restart, as McNulty went down injured and was unable to continue, with Charlie Wyke on to replace him.
Pompey were looking for a leveller, but Curtis could not find the target after rising to meet Walkes’ right-sided delivery.
They had a better chance when the visitors won position and Harness slipped a neat pass through to Marquis, who was unable to find the target.
And a spell of intricate short passes led to Brown finding the ball on the left, although his cross was not quite right for Harness.
Brown soon received the ball back again, though, and this time could not beat McLaughlin from a tight angle.
Luke O’Nien wanted a penalty at the other end after going down under pressure from Tom Naylor, but his appeals were immediately dismissed by referee Michael Salisbury.
And the official was equally unimpressed just moments later, when Maguire decided to theatrically hit the turf.
Jackett made a double switch just past hour mark, with Curtis and Andy Cannon making way for Harrison and Gareth Evans.
There was then a nervy moment as the ball flew around the Blues box and could not be cleared, but the danger eventually passed.
The final substitution for the visitors saw on-loan Scottish youngster Ross McCrorie replace Walkes at right-back.
And he immediately released Marquis with a great pass down the right. The striker squared for Evans, whose goal-bound effort was blocked by Alim Ozturk.
A cross from McCrorie was then diverted towards his own net by Leadbitter, but McLaughlin was able to claw the ball to safety.
Pompey continued to control possession as the seconds ticked down, although Sunderland remained resolute to see the game out.
Sunderland (4-2-3-1): J.McLaughlin; O’Nien, Ozturk, Willis, C.McLaughlin; Power, Leadbitter (c); Gooch, Maguire (Hume 87), McGeady (Grigg 81); McNulty (Wyke 49)
Goals: Willis 27, Maguire 39
Booked: McGeady, Maguire
Subs not used: Burge, Flanagan, Dobson, McGeouch
Pompey (4-3-3): MacGillivray; Walkes (McCrorie 73), Downing, Burgess, Brown; Close, Naylor (c), Cannon (Evans 62); Harness, Marquis, Curtis (Harrison 62)
Goals: Harness 22
Subs not used: Bass, Raggett, Haunstrup, Pitman
Referee: Michael Salisbury
Attendance: 29,140 (874 Pompey fans)