Ricky Holmes returned to haunt Pompey as Andy Awford’s 10-man side went down to a 1-0 defeat at Northampton.
The midfielder, who moved to the Sixfields Stadium in January after picking up The News/Sports Mail player-of-the-season award last term, scored with a beautifully-struck left-foot shot on 25 minutes as the Blues suffered their first defeat in eight games.
Until that moment of magic, Pompey were edging the encounter between the two in-form teams of League Two.
Ryan Taylor headed straight at Matt Duke in the ninth minute before Danny Hollands attempted an overhead-kick that went wide.
Paul Robinson then tried his luck with a header, while Josh Passley fired wide after he was set up by Matt Tubbs on 22 minutes.
However, it was Holmes who eventually found the breakthrough for the hosts, as he cut inside and fired a curling shot past Paul Jones and into the far corner of the net.
Pompey responded with a close-range volley from Tubbs that was stopped by Duke before Nigel Atangana burst through and fired over on the stroke of half-time.
In the second half, Pompey were finding their attacking play thwarted by the Cobblers’ resistance at the back, prompting a double substitution on the hour mark, with Atangana and Passley making way for Craig Westcarr and Andy Barcham.
Awford’s favoured 3-5-2 formation was swapped for a 3-4-3 system and, while it gave the Blues greater attacking impetus, it also opened up the game for both sides.
Holmes fired wide from an accute angle on 66 minutes, while Robinson had a header cleared off the line moments after Barcham broke into the box and crossed.
At the other end, Robinson had to be alert to clear substitute Maarc Richards’ effort off the line when Jones was robbed of possession on the edge of the box.
Meanwhile, Wes Fodgen – making his first appearance of the season after injury – nearly made an immediate impact after coming off the bench when he fired agonisingly wide from a Barcham cross with 11 minutes remaining.
Pompey tried hard to force the equalisr when Tubbs again shot goalwards.
But their hopes were ended in stoppage-time when captain Ben Chorley was sent off for a second bookable offence as Northampton claimed the three points.