The Northern Irish keeper has been handed an unexpected chance to impress Sir Alex Ferguson, after Barthez picked up thigh and hip injuries against Southampton on Saturday.
Carroll appears to have seen off the challenge of Ricardo, but is now looking to make the next step and play more regularly for The Red Devils.
The 25-year-old said: "My goal is to become number one at Manchester United.
"I know I have time on my side, but I want to get there sooner rather than later. It's the biggest challenge I have in front of me."
Carroll, though, knows he can still learn from French number one Barthez, as he added: "There are all the world-class players you can learn from, in particular Fabien, whose footwork is excellent."
