The year was 2015. According to MLB Pipeline Michael Fulmer and Steven Moya were the best prospects in the Detroit Tigers system. Scroll down to number 13 on that list, and sitting right behind Dixon Machado, you’ll find Grayson Greiner.
Without copying the scouting report verbatim, it says the same things you think it does. He’s got some defensive skill despite his size, and he has a lot to prove offensively. At the time though, he was the future of Detroit Tiger backstops. His only competition on that list was Arvicent Perez.