It's hard to believe that Stones had started only 22 senior matches in his career when he lined-up against Stoke in December given his calm, assured presence in the heart of Everton's defence during that game at the Britannia Stadium.
To use a well worn cliche he has an old head on young shoulders, but also has the exuberance of youth, having the belief to stride forward out of defence with the ball at his feet.
There is no question though that Saturday's match at the Emirates is the most significant game he will have played in so far, eclipsing even the Merseyside derby at Anfield in January.
That's not just because of the standard of opposition - any game at Arsenal is a big one - because of the prize at stake and the impact defeat may have on the rest of the season.
Most Everton fans who have seen him play so far will have no fears about Stones this Saturday, especially with the experienced Sylvain Distin alongside him.
His boss has also expressed his faith in Stones should Jagielka not make it (and there is every chance he still might).
Martinez is effusive in praise for the 19-year-old, tipping him to become on of the country's best defenders.
"John has been performing really well and has had two of the toughest tests you can have in the Barclays Premier League, playing against a striker like Andy Carroll, with his physicality and power in the air, and playing at the Britannia Stadium against Stoke.
"Both challenges were answered with two outstanding performances and John has been working really well. That’s what’s important.
"Over the course of a season you need players who are ready to come in and help the team and John has been a terrific example of that."
"I know how good he is and what a special footballer he is. He is going to have an incredible career.
"He is one of the most significant young players we have in the English game and I have seen him grow a lot in the last few months. He is someone who takes aspects of the game on board very quickly.
"He is a complete centre-half and in the modern game you need to be able to play from the back and have good distribution. John has that.
"On top of that, he is good in the air, very comfortable in one-v-one situations and he can defend within a unit.
"He is as good as it gets at his age."