Claudius Like @Clrnc said, if you're good enough, you're old enough. Not sure how you can look at what he's done in the limited opportunities he's had in PRESSURE packed conditions, both this weekend chasing a game and at Spurs defending the game, and think that we need to go overboard on easing him in. If that was the case then he should be playing with the youth teams.
Arteta clearly thinks he's good enough and let Vieira leave as a result. I don't want to rush him in either, but at this point, he's shown he's got the quality so I think it would be good for his development to start introducing more minutes and different conditions than just coming in as a sub. At the very least, it will give us an idea of how ready he is for certain circumstances when we actually might need him with the congested fixture list that is being referenced above.