Benford coached him in practice. Remember, Trey "decided to leave" about a month before classes started, the first year the NCAA moved up the start of organized practices. He tweeted how excited he was about the upcoming season after a practice (a day or two after TJ Taylor announced he was coming here), and after a meeting with Benford later that day, tweeted something else indicating he was very, very depressed.
EDIT: I just re-read my original post... Trey didn't play an organized game under Benford, but Benford was one of his college coaches for about 5 months. My fault for choice of phrasing.
https://www.youtube.com/watch?v=VS4QGEQaclk