The Pompey captain returned with a 45-minute outing against Cambridge United in the 2-1 Papa John’s Trophy defeat tonight at the Abbey Stadium.
Robertson has endured a testing period with a hip issue which required surgery, after making a flying start on the pitch at the start of the season.
The Cambridge game marked four months to the day since the 28-year-old’s last appearance against MK Dons.
It may have been a game played out on front of just 1,308 fans - but the occasion was still a special one for Robertson.
He said: ‘I can’t get the smile off my face.
‘I’ve been out on the grass for the past four or five weeks and building myself up.
‘I’ve just been trying to get myself ready for a night like this and I’m buzzing to be back out there.
‘I’m glad those problems are in the past now.
‘I’m just looking forward to the next three or four months of the season.
‘We’ve got some massive games coming up and I want to be playing my part until the end of the season now.’
The plan now for Robertson is to build up his playing time moving forward after a couple of weeks on the training pitch.
The former Rotherham man thinks it’s still a bit early to think about playing 90 competitive minutes.
The ambition now is to build up his sharpness to ensure he’s ready to play a significant part in Pompey’s play-off push over the second half of the campaign.
Robertson added: ‘I’ve got a good 45 minutes under my belt and you can’t replicate match minutes in training.
‘The plan was always to play 45 minutes and we felt it we felt it was best to start and come off.
‘I’ve been training for 10 days to two weeks now and the game came at a good time for me.
‘I was able to blow off some cobwebs, so now hopefully I can build myself up in training and coming on in games hopefully.’