And the Blues captain is adamant his squad is in a much stronger position this year to build a promotion challenge than they were 12 months ago.
Robertson recalled how there were just eight first-team players when he arrived for his first day of pre-season training after signing from Rotherham last summer.
That was the cue for a constant flow of triallists into Pompey’s training base ahead of the new campaign.
This time around Cowley already has a group of 18 first-team players in place, in addition to four first-year professionals and third-year scholars.
There’s been some angst at the lack of transfer activity, with Marlon Pack the only arrival so far.
In addition Aiden O’Brien has turned down Pompey’s contract to join rivals Shrewsbury, with Cowley without a senior striker to his name.
Robertson feels, however, the Blues boss is right to wait to get the players he wants with the squad better off than last year.
Speaking before news of O’Brien’s move to Shrewsbury emerged, Robertson said: ‘It was difficult last year when we came back with eight players.
‘There were literally 15-20 triallists coming in for the first few weeks, it was difficult.
‘The manager is doing his best to put a squad together and he’s not going to sign players just for the sake of it.
‘I think that’s understandable, because we need to be challenging.
‘This time around though, I think we are going to be more equipped.’
Robertson has looked on as Pompey took up options to give new deals to Louis Thompson, Marcus Harness, Jayden Reid and Jay Mingi.
In addition, new agreements have been signed by popular pair Sean Raggett and Michael Jacobs.
The Scot feels that gives his manager a good base to build from.
‘They were both massive players for us last season.
‘I was buzzing when I saw Raggs had signed and Crackers has a lot of quality at the top end of the pitch.
‘There a few others who had their options extended like Louis Thompson, who are going to be big players for us.
‘So we’ve got a good core there from last season that we can build on, hopefully with the signings the manager is going to make which can make us better than what we were last season.’