Portsmouth recorded a 2-1 win over Lincoln City at home on Saturday and are sitting at the top of the League One standings.
The 20-year-old Australian was at the heart of the Portsmouth team and played well to provide John Mousinho’s side a cutting edge in the middle of the park.
He is on loan at Portsmouth from Manchester City and Whittingham believes he is only getting better but feels he needs to just take that next step to complete his performances.
The former Portsmouth player and boss said on BBC Radio Solent: “Robertson is getting better and better but he still needs to pick up.
“He is almost there – just half at touch or a bit of a quick run and shielding the ball.
“He is nearly there to not only produce goals but be able to supply goals for others.”
Whittingham stressed that Robertson is a key player for the club given where he plays and his importance in creating goals for the League One club going forward.
“Those areas where he operates are tight because teams are coming here with a back five and four in front or four and a five or a four and a four – they are keeping tight distances.
“Once you punch through the midfield and you have the ball between their midfield and their defence, you want someone to take that on the turn and keep going forward.
“He is very capable of doing that.”
The 20-year-old has started five of Portsmouth’s eight League One games at the start of the season.
