And the Pompey skipper admitted he has a battle on his hands to regain his place in Danny Cowley’s starting XI.
The defensive competition is set to be stepped up further this month with a centre-back a transfer priority - and Blackburn’s Hayden Carter in the sights of the Blues boss.
Another striker is being sought, too, with Cowley stating he’s in the market for up to four new additions.
The space has been freed up in the playing budget to do that with departures this window, with Robertson believing some new energy within the ranks is what’s required.
He said: ‘The competition will only be a good thing.
‘It drives the standards in training when new boys come in and there’s new energy.
‘It can only benefit the team between now and the end of the season.
‘It’s going to be give a freshness to the team.
‘That’s what happens when new boys come in. You get a bit of a lift.
‘You know you’re going to have to work for your place in the team.
‘If your standards drop you’re not going to be in the team much longer. We know that.’
Robertson put four months of injury frustration behind him on Tuesday night with a return at Cambridge in the Papa John’s Trophy.
The 28-year-old has been sidelined with a hip injury which required surgery, after an impressive start to the season.
Cowley has sung the praises of Robertson on his return, but Connor Ogilvie and Sean Raggett have shone at the back in his absence and the skipper is fully aware he’s not guaranteed a starting spot.
Robertson added: ‘It means a lot, obviously, to know the manager trusts me.
‘Hopefully in the next few weeks I can build myself up.
‘I know I’m going to have to work hard to get back into the team, because the defence has been playing really well.
‘Connor has been excellent and Raggs has been excellent.
‘I just need to bide my time, wait for my moment and hopefully take my chance when it comes.’
A message from the Editor, Mark Waldron
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