The Blues boss has made no secret of his desire to bring in at least another three players before the transfer window closes at 11pm on Tuesday, August 31.
Cowley has already brought in 12 new faces this summer but remains on the lookout for a right-sided centre-back, a creative midfielder and another striker.
Pompey’s manager already has a squad of 22 senior players at his disposal – a number that does not include Liam Vincent and Jayden Reid.
Yet he’s convinced greater depth is needed to maintain a concerted promotion push this season.
Cowley named seven of his new arrivals in his starting line-up for the goalless draw at Doncaster Rovers on Saturday – Gavin Bazunu, Kieron Freeman, Clark Robertson, Connor Ogilvie, Ryan Tunnicliffe, Joe Morrell and Gassan Ahadme.
Two more were named on the bench – Shaun Williams and George Hirst, who were introduced to the action in the second half.
But Robinson, who was the quest pundit on BBC Solent for the Keepmoat Stadium game, agreed that new additions were required for Pompey to compete over a 46-game league season.
Despite believing the Blues’ best starting XI looked ‘strong’, he said there was room for further depth to be added.
‘You always hear the stories, don’t you, of the managers working overtime to try and put those final few details to their squad,’ said Robinson.
‘For myself, looking from afar, when I looked at the starting XI on the first day of the season I thought, “yeah, that looks a very strong, competitive XI for League One”.
‘But I think, as we all know, over a 46-game League One season how tough it can be with injuries, suspensions, loss of form – they can take their toll.
‘You do need a squad these days, you need a squad to perform at the energy levels that Danny obviously requires from his team and how they’re being required to press this season.
‘To do that, you need fresh bodies at certain times but also competition for places to make sure everyone is on their toes, everyone’s fighting, at the top of their form to win games week in, week out for Portsmouth. ’