Gareth Evans pounced on the ponderous Kyle McFadzean’s error, dispossessing the Coventry central defender.
Pompey’s skipper then strode forward and calmly slotted a right-footed shot past Marko Marosi to make it 3-1 in the 56th minute.
It also signalled Evans’ feat of netting in five-successive Blues seasons.
The ever-youthful Kanu was the last to register the goal-scoring achievement – eight-and-a-half years earlier.
Tuesday night’s encounter concluded with a 3-3 draw, an outcome to draw angry responses from the Fratton faithful, appalled at surrendering victory to their nine-man opposition.
Buried within the abject defensive display, however, was an encouraging attacking performance, epitomised by the recalled Evans’ contribution.
Since arriving as a triallist in the summer of 2015, the attacking midfielder has amassed 190 appearances, scored 33 times and won the League Two title and Checkatrade Trophy.
He has also now netted for Pompey in five-consecutive campaigns as he continues as a first-team regular.
Kanu actually registered during six seasons in a row, before his mutually-agreed exit in the summer of 2012.
Recruited as a free agent by Harry Redknapp on the eve of the 2006-07 campaign, the Nigerian striker would total 28 goals for the Blues.
Among them was the finish which earned Pompey the 2008 FA Cup – the first time they had captured the trophy in 69 years.
During his six-season stay, Kanu scored in each, although tallied just three times in his final two campaigns.
The goal which signalled the feat of registering in five-consecutive terms arrived in a 2-1 defeat at Nottingham Forest in January 2011.
More recently, the popular Conor Chaplin registered during four-successive years, yet that run came to an end shortly before his departure for Coventry in August 2018.
A substitute appearance in the Carabao Cup against AFC Wimbledon signified his first and final Pompey outing that term, while he failed to net.
Before Kanu, youth-team product Gary O’Neil scored in seven-consecutive seasons from 2000-01 until 2006-07.
While Matt Taylor’s feat involved six campaigns in a row, before sold to Bolton in January 2008.