Millsap had played two full seasons and was nearly 24yrs old before he started game consistently, and that only occurred because of injuries to Boozer. Even though he played arguably better than Boozer as their starting PF, and even with all the garbage coming from Boozer and all the attempts to trade him- Millsap has not started a single game this season.
CJ Miles got starts when he was young due to injuries to AK47 and the lack of a SG, eventually Sloan decided to start two PGs (Fisher + Williams) rather than continue with Miles or Brewer.
Basically, necessity is the mother of playing rookies.
When we had a hole at SG due to Larry Hughes's injuries, Mike Brown tried Shannon Brown, Dan Gibson, and eventually decided to go with a Sloan reject - using Pavs (who was just 22yrs old when Mike Brown was starting him at SG).
There was no necessity to start Hickson. We could have gone with a 3 man big rotation and gone small while continuing to allow him time to acclimate to the league. Ferry made the decision to force feed him in to the starting lineup in spite of the fact that he'd done nothing to deserve the opportunity, and we're fortunate it didn't backfire. We're also very fortunate that JJ has bought in to the garbage-man role and isn't trying to do too much ala Shannon Brown.
Anyway, Sloan is a good coach, but personally I think he's lost touch with his team numerous times and it's basically cost the Jazz entire seasons. Their level of play has been very up and down playing with the top-contenders some weeks, and playing like an 8th seed another.
Kirilenko had people talking about quadruple doubles when he came in to the league, and while Utah decided to pay him like a superstar, he never developed in to one. He had DPOY level talent, but he's more of a defensive specialist. In fact he hasn't seemed the same since the Jazz brought in Boozer. Speaking of Boozer, Avon mentioned that players can just improve defensively over time, but Boozer is proof that is just not the case at all. They need to be pushed to play D and Sloan hasn't been able to get Boozer to step up his D. Mehmet Okur would be more than just a gimmick if he actually played some defense.
Illgauskus on the other hand has become a very solid defender, even with players like Gooden protecting his back rather than a super shotblocker/defender like AK47.
If Sloan was stressing defense like Mike Brown and getting his guys to step up their defense like Mike Brown, then they've had the offensive fire power needed to do some damage, but they didn't so they don't.