Barkley completed his £15million switch from Everton to Chelsea yesterday, signing a five-and-a-half-year contract.
The midfielder was out of contract at Everton this summer and has not played this season due to a serious hamstring injury.
Shearer has no doubts over the quality of Barkley but says he must prove it on a consistent basis if he gets the game time at Chelsea.
“We’ve been talking about Ross now for a number of years to say what a talent he is,” the Newcastle legend said.
“He’s now got an opportunity once and for all I think to actually go and prove it.
“He’s got the ability, we haven’t seen it anywhere near enough.
“Whether he’s going to play there or not is a different matter.”
Shearer’s colleague and former Liverpool midfielder Danny Murphy says the signing of Barkley is not a gamble from Chelsea.
And he reckons he will thrive in front of goal when given the opportunity by Antonio Conte.
“The thing is, £15million is not a big risk,” Murphy said in response to Shearer.
“I know they will be paying him a few quid, but in a good side like that, he can score goals.”