Rooney celebrated his 28th birthday on Thursday on the back of another sensational performance for Manchester United.
Although the striker did not score against Real Sociedad on Wednesday night, he was responsible for the second-minute goal that has moved the Red Devils to within a win of the 10-point total Sir Alex Ferguson used to use at the benchmark to qualify for the last 16 of the Champions League.
Even Ferguson admitted Rooney was in electric form this season, and claimed earlier this week he would not have considered selling him had he been producing such high-class performances on a regular basis last term.
But, according to Carrick - a team-mate for both club and country - the scary thing is Rooney can do more.
"I am sure he is looking to improve," Carrick said.
"He's getting on, isn't he? But look at Ryan Giggs. What he did on Wednesday was incredible. He goes from not playing for a bit to finishing a game like that - it sets an example to everyone.
"They say you are just getting into your peak at 28. If Wayne wants to can carry on playing on for a long time yet I am sure he will improve - and he is playing well at the moment."
Even now Ferguson's stance towards Rooney has softened, it does appear the striker has been wounded by his former manager's words.
The former Everton man confirmed he has not spoken to Ferguson since the end of the season and has already underlined how much he is relishing being played in a forward role by new boss David Moyes.
Yet Carrick rejects the theory Rooney has got his focus back.
For he insists it was never lost in the first place.
"You cannot question his focus at all," the 32-year-old said. "As players, you have good spells and spells where it doesn't quite go for you.
"He is having a great one at the moment and I am sure it will continue for a long time."