That's the majority of his full season experience.
I'm talking about literally like 20ip here.
2012 was his first year pro, and at 17 he was great at high rookie and A- levels - already way ahead of all but the best prospects:
9gs, 43.2ip, 27.2k%, 8.3b%, 2.27er, 3.12fip
This is similar to what, say, Thor put up at the exact same levels - but Thor was over a year and a half older.
Then in 2013, at 18 in full season ball, he started off the season on ridiculous fire:
7gs, 33.0ip, 33.1k%, 3.9b%, 2.43era 2.83fip
Then got hurt his next start, and tried to pitch thru it for 2 more starts before going for surgery (you can really see it in his command):
3gs, 9.0ip, 18.4k%, 12.2b%, 17.00era, 6.89fip
Then he came back the next year, as a 19yr old in A+, and started off like this:
5gs, 12.2ip, 27.0k%, 12.7k%, 9.24era, 5.14fip
And then got his game back together and dominated again (again, you can really see it in his command):
3gs, 10.1ip, 36.6k%, 2.4b%, 2.61era, 2.33fip
The next year, he was a dominant closer in MLB at 20.