I remember in about 2013/14 when Adam Milne and Matt Henry were the next big thing after Boult and Southee, some NZ posters were not particularly concerned about Wagner missing tests.
Interesting note on that Hobart game with Bracewell, that was also the tour that Dean Brownlie killed it, and again in SA on a disaster tour in 2013, his career went down a fairly similar path following that
Adam Milne has never played a test. Henry made his debut in England 2015 taking Wagner's place. Henry was dropped soon after, but not replaced by Wagner, but by Bracewell.
Wagner in 2014 took wickets at 27.36 and in 2015 at 26, and that saw him DROPPED. It was an error, Henry was understandable to trial as he deserved a crack, but Bracewell was merely NZ searching for an all-rounder, and it was a total stuff up in hindsight, even at the time, I thought the trial opps were going on far too long keeping Wags out,
especially for Bracewell. Bracewell was obviously not going to be a success. There were concerns about runs, so Bracewell was tried out as an allrounder. It failed as an experiment.
Henry just bowled too short, but friendly short, in his first NZ spell. In England of all places. It was strange. Stokes smashed him. Wagner should have played test 1 in Australia in 2015, instead Henry did, then replaced by Bracewell. Wagner missed the England tour, the Aus tour, and one of the home tests vs Aus.