The 20-year-old midfielder joined Portsmouth on a season-long loan from Manchester City in the summer and has managed to establish himself in the starting line-up.
Robertson has featured in 20 games in all competitions for Portsmouth and has turned some heads with his performances.
Pack stated that he understood how good the Manchester City talent was when he first saw him on the training pitch and stressed that the midfielder is growing week in and week out.
The Pompey captain also added that Robertson is in such good form that it is impossible to point out a mistake in his game and he thinks that the Manchester City loanee is starting to show his real quality.
“I think it is down to him; it generally is”, Pack, asked how far Robertson can go in the future, said on BBC Radio Solent.
“From what I have seen when he first came in, you can naturally see on the training pitch what a fantastic footballer he is.
“He is growing week in and week out, putting in performances where I do not think you can even question whether he could do this or that better.
“He just seems to be in a real state of flow where he is showing the real quality of Alex Robertson.”
Robertson will be hoping to continue his form until the end of the season and catch the eye of Manchester City boss Pep Guardiola.