Look at a guy like Gary Harris for the Denver Nuggets.
6'4'' 210
21 years old
Averaging 12 points, 3 rebounds per game in his second year out of Michigan State. Started all 76 games for the Nuggets. Led them in minutes and games played. Shoots 35% from the 3pt line.
What are the odds Buddy doesn't turn out better than Gary Harris? Who many people consider to be a pretty solid young player, even at 6'4'', in the NBA.
I just don't see how it's possible at this point that Buddy doesn't give you significantly more than Gary Harris, who is a starter putting in 12 per game. If he can do that now, Buddy should be able to come in and average 15+ per game for the right time.
And, if that is true, he should be a top 5 pick.
No rookie age 23 or older (on Feb 1 of his rookie season) has averaged 15+ PPG in more than 20 years. Technically, one did:
Reggie Williams averaged 15.2 PPG in only 24 games in 2009-10 after signing a couple of 10-day contracts. Was he top 5 pick worthy?
Lowering the bar, only two rookies age 23+ have averaged more than 12 PPG in the last decade: MarShon Brooks and Al Thornton. Two years later, Brooks was bouncing around the D-League and Europe; he's now in China. Three years later, Thornton went to Puerto Rico, then China; he's now in the Philippines.
It's rare for older rookies to step in and average 12+ PPG, let alone 15+ PPG. When it happens, it's with maxed-out talents given the green light on really bad teams. Rookies who average 15+ PPG are typically younger guys who were so talented that it made no sense for them to stay in school longer.
That's not to say that a 23-year-old rookie can't eventually succeed, but even older rookies need time to adjust. Only three second-years players age 24 or older have averaged 15+ PPG: Thornton, Wes Matthews, and Chandler Parsons.
That's the history working against Buddy.
I'm sort of just playing devil's advocate here, but I do think you're underestimating the age factor as well as how big of a jump it is from college to the NBA. One problem with the "If Harris can do that, then Buddy can do this..." assumption is that Gary Harris is nine months younger than Buddy. I'm not saying Harris is better than Buddy, but to put things in perspective, how dominant would Harris be in the NCAA next season as a 22-year-old? Buddy gets compared to Redick, but it took Redick years to become a really valuable role player after destroying college competition in a senior season comparable to Buddy's. Also, no one would trade anything close to a top 5 pick for Gary Harris right now, so "better than Gary Harris" isn't a reasonable threshold for top 5 worthiness.
I believe Buddy's risk of being a complete bust is really low, and that's he's capable of improving significantly, but I completely understand why there are reservations about him in the top 5 range.