I think we all agree Whiteside will take some time to develop. Big men always take longer to mature... like Bynum who is still learning. His measurements are good, it'll all depend on how he works out. Thats the only way to tell
He's rail thin
He's 21
He has a low basketball IQ
There are questions about his maturity and work ethic
None of those are deal breakers, but taken together they are a red flag.
Being rail thin isn't a problem for a young kid but at 21 you have to wonder why he hasn't added much weight already. Similarly, a low hoops IQ is always a bit of a red flag, but coupled with questions about whether he'll work hard it makes you that much more nervous.
Again, it's one thing to say, "he's got great measurements - he just needs to gain weight" and the reality which is that guys that come into the NBA at his size and weight RARELY gain significant weight. And so they learn to be successful without being a traditional big that can man defend in the post or score in the blocks.
IMO the biggest needs for the Kings are:
1) A second star to pair with Tyreke, regardless of position but hopefully a big
2) Low Post offense
3) Low post defense
4) Rebounding
5) Shotblocking
In my opinion, Whiteside would definitely provide the last one. I think being able to alter shots inside is important but I don't think you need a great shotblocker to be a good or even great defensive team.
And he will be a decent NBA rebounder if he can deal with getting banged around a bit inside. He'll never be a box out and secure the board type of guy, but with his length and athleticism he can go get rebounds.
That said, I don't see him providing any of the biggest three needs I see for this team.