The Braves simply don't have a choice but to bring in Teaheran as a fill in for Brandon Beachy. I don't share your concerns as his spring performance earned him his spot initially as the Braves mid-reliever and possibly the 5 starter. I am not relying on spring stats but the guy I saw this past month was not the guy who had a down year last year. All reports show that his command has drastically improved and he is starting to develop his breaking ball and changeup into bona fide out pitches. Fredi Gonzalez had a lot of patience with Mike Minor last year and it took a couple of months to pay off but Minor finally seemed to figure himself out resulting in a really strong second half. At this point getting your top pitching prospect big league innings in the 5 spot is the next step in his progression to becomimg that 3 or 4 starter the Braves hope he can be. Teaheran will eventually get comfortable, its not like he is expected to be the ace of the staff. Most of his coaches are already saying its kind of a now or never for him and he has nothing further to gain from time in AAA. I think his only problems at this point are between the ears because his stuff is definitely there.
Nobody else is ready as Sean Gilmartin is probably a full AAA season away from competing. I also don't think Wren has a track record of yanking guys onto the team before they are ready. The guys he has pulled up the last few years have become everyday players immediately. (Heyward, Freeman, Kimbrel, Medlan)