If that were the case, people would still be willing to see what he's got in a couple of April starts, just like they were before ST.
Happ had one of the best springs in the league last year, along with Phil Humber, Brandon Maurer, and Lucas Harrell. Mike Minor, Bartolo Colon, Homer Bailey, and Kris Medlen were amongst the worst, with some pretty putrid stats.
I'm not saying Happ will be good, but history has a good lesson to teach you about overreacting to spring training.