He doesn't read defenses and adjust so well yet, and doesn't have the nifty moves and cuts, and doesn't have the hands and "go get it" ball skills that Kearse and Tate do.
Speed, speed, and more speed though, for sure.
Plus he's a reasonably big body, 220ish, and I was surprised he hadn't been a bigger factor on Special Teams before. It seems like "it's about time!" on that one.
Special Teams will be how he sticks with this team, if he does. Maybe a couple more years, like Tate needed, and he'll get enough polish as a WR to be a bigger contributor.