In short: It was a bad year for him playing with and against established players. As this author puts it, his season highs were not as high as advertised and came in mostly irrelevant games, and when it mattered and better players were healthy he barely played.
I don't agree in all points, e.g. he neglects to mention skills Jennings improved by all accounts, due to good (assistant) coaches in Rome tutoring him.
And I would side with Jennings that part of it was he and his agent just picked the wrong team stacked with more experienced guards. But it's definitely worth a read of a contrarian opinion for all fans of his game and potential. Especially regarding a player who accuses other players to be "all hype".