Not surprised at all by this chart. Kelvin has been one of the most inefficient WRs in the NFL considering his usage. PFF also grades every play and as we've seen, Kelvin has some pretty frustrating moments. It also doesn't help that a lot of his numbers have come in garbage time.
With that being said, he's alone in this offense and was put in a pretty poor situation considering how raw he was/still is. A lot of his mistakes are correctable and I'm very excited for the future.