Thanks for clarifying. I'm not quite sure I fully understand what you're saying though. Taking names out of it--Barkley's a special case--are you suggesting that a productive rookie season doesn't make a prospect any less likely to bust than a rookie?
I'm confident that a player is much less likely to bust after flashing during their rookie season. Plenty of backs who rush for 1,000 yards as a rookie, for example, will go on to bust. But they will bust at a much lower rate than a generic rookie. Do we disagree there?
Edit: So maybe Kamara isn't proven, per se, but he's a lot more proven, and thus safer, than a rookie. (And I'd totally make an exception for Barkley here. I don't think he's as safe as Kamara, but will concede that he's as safe as it gets for a prospect.)
I think I am somewhere between your view and FreeBaGel view on this.
I agree that the rookie showing that what they did as a player in college translating to the pro level is a huge step forward. That is the main question I have about all rookie players. Will what they did in college transfer to a higher level of competition?
The rookie showing that compared to one who doesn't is a big deal.
That said, it doesn't mean that what the player did as a rookie is sustainable. It also doesn't mean that a rookie who didn't produce in their rookie season is a bust either. Thats why I generally give a rookie 2-3 seasons before I feel completely comfortable with who they are as a player.
To give some recent examples.
Melvin Gordon didn't produce all that well in his rookie season. He did in his second and 3rd seasons though.
Todd Gurley did well as a rookie but then not as good in his second season. Now having his best year in his 3rd season.
Both players have proven to be tier one RB for fantasy in my view over their first 3 seasons. They just took different paths to getting there.
Gordon may have been considered a bust based on his rookie season. Some may have thought Gurley was a one year wonder after his second season.
There are more extreme examples than these. Just sticking to some high profile players. There are examples of a player doing well as a rookie and then fading from relevance every season after that. I think this is more rare than a player doing well as a rookie and going on to have a successful career, but it does happen some times.
On the flip side of this, for RB the rookie season is the worst performing season on average of the first six years of their career (which are the most productive seasons for a RB on average). There are a lot of different reasons for this unrelated to the RBs talent. Injuries, pass protection, sharing time with an incumbent being the main ones, it just generally takes awhile for a player to earn the trust of the coaching staff to get as much opportunity as a rookie as the player will in following seasons.
We cant ever know how things will play out for any rookie player before the fact. It requires a leap of faith, a belief in the player at some point.
The player going into their second season does give you more information at the NFL level to work with. More proven than a rookie who hasn't played in the NFL yet. Still not enough data for me to consider the player proven however, I want two seasons of data to work with and ideally three before I feel comfortable with projections for them.