What is Berrios doing better this season that is making him more effective than he was against inferior competition in A ball?
A year ago, Berrios spent the weeks leading up to the season being used sparingly out of the Puerto Rico bullpen in the WBC. When he did join the CR rotation later in April, he was still being stretched out. He had stuff, but he also tended to lose some composure/focus when things started going bad in a particular inning (as often happens at low-A).
I haven't seen him since March in ST, but I would speculate that having a full spring training to prepare for a rotation role and another full year of physical/mental maturity may combine to see the improved results this season. Hopefully, a more 'normal' year also will mean having the stamina to be more effective through to the end of the minor league season.
I'm really glad to see him having this kind of success this year.