Better physical and mental shape. He tanked at the combine, and by the time the draft came around, he was a pariah. 4.3 does seem faster than one would expect. But, in all likelihood, he should probably be considered of average speed. Zay clocked a 4.45 at his combine, which didn't raise any eyebrows. I would be interested to see what his top speed actually is, which I don't believe anyone really knows. But, before his character issues, his school expulsion, and tanked combine, he was considered a top prospect. If 4.3 seems unlikely, it seems more unlikely that he had achieved that much hype while being "slow."