The problem is that both of your rookies are pretty awful. One needs 5 pops in ID to be respectable there, the other needs 4 in IS to get to respectable. Either way, you can likely replace both of them with 19yos who don't have nearly the issues they do, for next to nothing (seriously, I had to fire a 19yo who was better than both of them this week, because nobody wanted him). If I absolutely had to choose one of the 18yos, to train, I'd probably pick the second one, and curse him every week the first season I trained him.
That said, your 20yo guys aren't bad, and if I were in your shoes, I'd probably focus my training around those guys, the backup PF perennial allstar guy in particular.
Now, these two:
STARTING PF
Weekly salary: $ 7 244
Age: 24
Height: 7'0" / 213 cm
Potential: MVP
Jump Shot: strong Jump Range: average
Outside Def.: awful Handling: atrocious
Driving: inept Passing: pitiful
Inside Shot: respectable Inside Def.: proficient
Rebounding: respectable Shot Blocking: average
Stamina: strong Free Throw: inept
Experience: awful
STARTING C
Weekly salary: $ 6 292
Age: 26
Height: 6'11" / 211 cm
Potential: perennial allstar
Jump Shot: awful Jump Range: awful
Outside Def.: respectable Handling: pitiful
Driving: awful Passing: strong
Inside Shot: respectable Inside Def.: proficient
Rebounding: average Shot Blocking: strong
Stamina: average Free Throw: pitiful
...can play SF in a LI offense until your trainees come up. If you choose to do 2-position training, the 24yo can get some minutes at PF, but I wouldn't waste any time training that 26yo dude.
Just my 2 cents.