The former Crystal Palace and Birmingham front man, who was a pundit on Saturday night’s EFL on Quest show, believes a remedy at the back is desperately needed otherwise the Blues boss could find himself under increasing pressure.
His remarks come after Pompey earned a 2-2 draw from their 540-mile round trip to Accrington.
There were plenty of positives to take from the game, with the Blues edging possession, recording 19 shots and showing the strength of character to earn a point through Marcus Harness’ 86th-minute tap-in after going 2-1 down with 13 minutes remaining on the clock.
However, the two second-half goals they conceded illustrated that Cowley still has plenty to think about defensively.
He reverted to a back four at the Wham Stadium after experimenting with three centre-halves in recent weeks,
But the goals Pompey let in took their goals-against tally to 10 in three games and a staggering 26 in 11.
The Blues also sit 16th in the League One table.
And Morrison, believes it’s a problem area Cowley needs to swiftly get on top off if he is to keep the pressure at a manageable level.
He said: ‘They’ve conceded 10 goals in their last three games.
‘We all know Portsmouth can score goals but it hasn’t been good enough defensively.
‘They need to stop shipping all these goals in because we know they can score goals with Curtis and Harness going forward.
‘But they need to start defending because the pressure will start to mount on Danny Cowley. ’