Pompey’s winning run was brought to an end with a 2-1 defeat to Peterborough at London Road.
It was a fairly even contest, but a couple of fine deliveries from Marcus Maddison ultimately proved the difference.
The Posh midfielder provided the assist for Jack Marriott to open the scoring and then saw his free-kick headed into his own net by Matt Clarke.
Conor Chaplin came off the bench to pull a goal back for the Blues, but they were unable to find a leveller.
Kenny Jackett made two changes from the side that beat Southend at Fratton Park on Saturday.
Curtis Main made his second league start of the season in place of Brett Pitman, who missed out with a hamstring injury.
Matty Kennedy also returned in an attacking role wide on the left, with Kyle Bennett dropping to the bench.
But it was Jamal Lowe on the opposite flank who caused the hosts plenty of problems in the early stages.
One promising move saw him surge half the length of the pitch and whip in a cross that was met by Kal Naismith and deflected past the post.
And Naismith was then left alone at the far post to head stand-in skipper Gareth Evans’ corner back across goal, although the Posh defence were able to hack clear.
Peterborough soon began to settle, however, and dominate possession without creating too much of note.
They did go close on 18 minutes when Danny Lloyd threaded a pass through to Gwion Edwards, who lifted the ball over Luke McGee and against the crossbar.
Then, after Ben Close’s effort had been blocked, United charged straight down the other end and McGee – who along with Christian Burgess was facing his former club – palmed behind Maddison’s deflected effort.
But it was Pompey’s turn to threaten more towards the end of the first half and a fierce attempt from Main clipped the outside of the post.
There was one sensational cross-field pass from Oliver Hawkins to pick out Kennedy on the left, although the winger cross was claimed by keeper Conor O’Malley and the sides went in level at the break.
Half Time: Peterborough 0 Pompey 0
The opening to the second half was also a pretty cagey affair, with little action to get either of the goalkeepers’ gloves dirty.
Maddison’s free-kick – given for a foul on the edge of the box by Kennedy – was headed clear by Main.
The striker was then involved at the other end of the pitch, sliding in but unable to make contact with Naismith’s teasing low delivery.
Naismith soon had a chance of his own and finally forced O’Malley into a meaningful save with a powerfully-struck effort from the edge of the box.
But it was Peterborough who finally broke the deadlock just before the hour mark when Maddison sent in a low cross from the left and Marriott arrived to bundle the ball home.
Jackett responded by making his first substitution, as the hard-working Main made way for Chaplin in attack.
It was Posh looking more likely to add to the scoring, however, and Hawkins had to turn one effort just past his own post, while Steven Taylor fired narrowly over from a corner.
But they needed a helping hand to double their advantage on 70 minutes after Burgess had been booked for a foul on Maddision.
It was the midfielder who dusted himself down to take the free-kick, which was inadvertently turned into his own net by Clarke.
Chaplin almost reduced the deficit soon after, although his miskicked shot was cleared from the line by a well-placed Anthony Grant.
But CHAPLIN did find the target on 78 minutes, sliding the ball into the net after O’Malley could only parry clear Danny Rose’s effort.
There were a few nerves starting to show for Peterborough as they tried to hang on to their now slender lead.
But for all of Pompey’s attacking intent, they were unable to test O’Malley again as time ran out in the search for a point.
Peterborough (3-5-2): O’Malley; Baldwin (c), Taylor, Tafazolli (Hughes 46); Lopes, Grant, Maddison (Anderson 85), Doughty, Edwards; Marriott, Lloyd
Goals: Marriott 58, Clarke 70 (og)
Booked: Grant, Edwards
Subs not used: Bond, Penny, Forrester, Kanu, Miller
Pompey (4-2-3-1): McGee; Evans (c), Hawkins, Burgess, Clarke; Close, Rose; Lowe, Naismith, Kennedy (Donohue 81); Main (Chaplin 64)
Goals: Chaplin 78
Booked: Burgess
Subs not used: Bass, Thompson, O’Keefe, May, Bennett
Referee: Craig Hicks
Attendance: 5,217 (841 Pompey fans)