At 6'8 235 with a 7'3 wingspan, Hayes would have been pegged as a 3.5 tweener a generation ago - not big enough to be a 4, not perimeter oriented enough to be a 3. These days, he has great size for a 4 and he might even be best used as a small-ball 5. He's about the same size as Draymond Green. Hayes has the long arms and the thick base that would at least give him a chance of holding his own on the block against bigger offensive players while playing as a 5 on offense would give him an advantage in terms of quickness and being able to take slower defenders out on the perimeter.
The match-up with the wide-bodied Bryant (6'10 240 with a 7'5 wingspan) would be a good test for that theory. Hayes didn't play much on Bryant and when he did he really had trouble banging with him on the block without getting called for a foul (although the refs did seem to have a pretty tight whistle in this one):
The more promising aspect of the match-up for Hayes came on the other end of the floor, where he was able to face up Bryant and beat him to the basket:
The difference between when Bryant was guarding him and when a smaller and faster defender like Juwan Morgan (6'7 205) was noticeable:
Hayes just isn't as comfortable trying to bully smaller defenders on the block. In this sequence, Indiana freshman OG Anunoby (6'8 215) swats the hell out of him when he tries to post him up:
Anunoby also buried a few 3's on Hayes on offense and he looks like he will be a real interesting prospect in a few years.
The concern is that if you are playing Hayes as a 4 he doesn't really have a huge edge in size and he's not comfortable scoring over smaller defenders. Nor would he would have an edge in quickness against them and he's not a great three-point shooter (28.6%) so he's not offering much spacing from that position. In essence, he would pretty much be just a guy and there's no reason to draft someone whose just a guy in the first round.
The key with Hayes is can he consistently guard bigger offensive players because the best way for him to score is to take bigger defenders out on the perimeter and face them up. Purdue's massive front-line should be an interesting test for him in that department.
Bryant is pretty much the exact opposite in terms of his strengths and weaknesses as a prospect. He's the rare young big man with an incredibly developed feel for scoring with his back to the basket and he's already a huge problem for most NCAA teams in terms of being able to handle him on the block:
Bryant has all the moves and it's almost impossible for most NCAA big men to cover him 1-on-1:
Bryant might have been pegged as a traditional 4 a generation ago but he's purely a 5 in the modern game, which means he needs to be able to protect the rim. That's an area of his game where he has a lot of room to improve on - he has the bulk and the reach but he's not a great athlete so he has to position himself perfectly and anticipate what the offense is going to do. If he's going to react slowly, he might as well not even be there:
The first question that any big man needs to answer in the modern NBA is can you move your feet? If you can't, you are going to get mercilessly attacked in the pick-and-roll and that's my #1 concern with Bryant. Watch how slowly he hedges and recovers in this sequence:
I'm just not sure if Bryant is ever going to be fast enough to guard in space, which puts a pretty dramatic ceiling on how good he can be at the next level. He's a guy who might be better in the NCAA than he will ever be in the NBA.