Throwing my two cents in the forum....
1. I would not worry about Super 2 and saving him another year before hitting free agency. I do not say this with regards to controlling him, but it is due to the fact that the new collective agreement is going to throw this idea out the window. MLBPA has taken notice of the delays with young ready to go guy such a Longoria, Wieters, Strasburg, etc... and they are going to put a squash to it. My gut feeling is that acrude dating system is going to be reduced and it will not factor one bit whether Britton starts in April or June.
2. As in life, everyone is on thier own biological clock. Some guys need 1,000 at bats and others can use 400 at bats. Some guys need 500 innings and others need 200 innings. It is just life and there is no set rule in place that make one better than the other. It will always be based on factors that you can never set in stone; it is a heavy shade of grey. I do not like what Tampa does to some of thier prospects because they simply do these measures as a manipulative way to keep payroll down for years. They waiting too long last season to keep a prize piece in the minors and he was ready. They may have keep some guys down too long now. It is fine if you do it for development, but at the cost of simply holding guys down to cheap cut them is not something I take lightly.
Overall, I am not saying that Zac is ready. I am saying you always take the best 5 that are ready for the majors. What can Britton show at Norfolk besides the command he already carries in spring training. Chris Tillman should get a chance ahead of him, but I still wonder out loud about Brad. He has looked so-so and this is being nice. You can bring him up, but with options on the table you can yank him quickly for Britton.