Portsmouth 2 Man City 1: Portsmouth substitute Kanu put his team back on the winning track with another late decider after Pedro Mendes had opened the scoring early on before suffering an injury courtesy of Joey Barton.
Mendes who hit two goals — including a late winner — to beat City last season at Fratton Park, struck from 25 yards after just four minutes but was injured when Barton stood on his heel in the 41st minute.
Pompey manager Harry Redknapp was banished to the stands after allegedly swearing at referee Mike Dean in the tunnel at half-time and saw Bernardo Corradi grab a 62nd-minute City equaliser before Kanu's latest heroics nine minutes from time.