According to NFL.com, Pettis is a solid secondary receiving option who has spent time on his craft and has the ability to attack and uncover on all three levels. Pettis lacks physicality and could struggle to handle in-your-face press corners, so he may see snaps from the slot. While his punt return talent solidifies his draft standing, his ability as route-runner combined with his smooth pass-catching should give him a long, solid career. Indeed, as the Sports Xchange reminded readers, Marquise Goodwin began last season as a one-dimensional deep threat who transitioned into a quality route-runner at about the same time Jimmy Garoppolo arrived. So there's room for a speedy guy like Pettis even if Goodwin is on the field.
If there's a transition period (and it seems likely there will be), that's fine, because Pettis should be able to help a pedestrian 49ers return game right away. Still, being limited to return work as a rookie wouldn't be conducive to high-end fantasy production.
2018 Bottom Line
I may have understated that downside a bit. The truth is, Pettis is a strong dynasty prospect who shouldn't be rostered in redraft teams until and/or unless he finds himself in a position to make a significant, consistent contribution. He's not there yet.