Casey Gillaspie couldn't find himself at the plate at all in his time in the Arizona Fall League. The 2014 Rays first-round pick finished with a .191/.273/.281 hitting line along with two home runs. He actually finished better than his time in Class A-Advanced Charlotte, but that isn't saying much considering he hit just .146 and had a 51 wRC+ there. In either case, he was not performing up to par.
In my 20/20 hindsight, maybe Gillaspie just wasn't ready to face this new tier of pitching? A majority of the pitchers he faced spent 2015 in Double or Triple A, meaning they have at least one more year of experience in professional baseball, and possibly even more. I speculated that the team sent Gillaspie to the AFL to accelerate his growth, but looking back, Gillaspie didn't appear ready.
If Gillaspie starts 2016 any higher than Charlotte I will be thoroughly surprised. His stats from Charlotte last year as well as the AFL don't warrant a promotion to Double A to me. He clearly needs more time to develop at the Class A-Advanced level before he should be promoted to Montgomery.
On the other hand, his struggles could be coming from injury. He did miss more than a month and a half after breaking his finger just five games into his stint at Charlotte. Gillaspie flashed the plus raw power we all hoped he would while he was with Class-A Bowling Green, hitting 16 home runs in 64 games (one every four games) while still maintaining a respectable .278 average. After he returned from injury, his average was just .185 and he only hit one home run over 14 games, including the Florida State League playoffs. While correlation does not equal causation, it still makes me wonder how much Gillaspie's finger bothered him hitting.
It's not like Gillaspie is an inept player; he clearly can perform. The matter is what affected his performance when he reached Charlotte and Arizona. Increased competition, injury, or even both could have caused him to regress like we have seen. Obviously, myself and the rest of Rays fans hope Gillaspie blossoms into the power-hitting first baseman he was pitched as after he was drafted, but it remains to be seen whether or not he reaches that echelon as the 2016 season nears.