yep it's there, although a little convoluted and unobvious!
go into the gameplay settings and the first section is for
Global Sliders and you'll see all the gameplay sliders (like gamespeed, free throw difficulty.. etc)
you need to browse across to the
User section of gameplay, note that there's also a
CPU Slider section which you can browse to as well.
anyway, in the
User slider section, go to
User Substitution Frequency: and set it to 50 for auto-subs. at 0 it is up to the users discretion for substitutions, but set at 50 it'll do subs for foul and fatigue trouble, etc.
i hvae this on Xbox, but i doubt the menus change at all between the different platforms...
Also here is a general gameplay settings for the most realistic gameplay:
http://www.nba-live.com/nba2005/sliders.php
Optimised for 12 minute quarters on the harder difficulty settings
GLOBAL:
Game Speed: 36
Free Throw Difficulty: 65
Boundary Force Field: 60
Injury Frequency: 50
Fatigue Effect: 50
Charge/Block Foul Frequency: 55
Shooting Foul Frequency: 25
Reach-in Foul Frequency: 12
In-air Collision Foul Frequency: 75
USER:
User Steal Ability: 40
User Interception Ability: 34
User Shot Block Ability: 0
User Dunk/Lay-up Block Ability: 0
User Freestyle Effectiveness: 45
User Dunk vs. Lay-up Frequency: 40
User Substitution Frequency: 0 (50 for Auto-Subs)
User On-ball Defense Assist: 42
User Offensive Rebounding: 40
User Defensive Rebounding: 75
User Fakeout Discipline: 100
User Short Range Shooting: 50
User Medium Range Shooting: 50
User Long Range Shooting: 50
User Dunk Percentage: 50
User Lay-up Percentage: 50
User Adjusted Shot Percentage: 50
User On-ball Defense: 50
User Poor Release Shot Percent: 50
User Double-team Effectiveness: 50
User Pro Hop Effectiveness: 30
User Drop Step Effectiveness: 50
CPU:
CPU Steal Ability: 34
CPU Interception Ability: 10
CPU Shot Block Ability: 0
CPU Dunk/Lay-up Block Ability: 0
CPU Freestyle Effectiveness: 40
CPU Dunk Frequency: 40
CPU Substitution Frequency: 50
CPU Offensive Rebounding: 40
CPU Defensive Rebounding: 75
CPU Fakeout Discipline: 50
CPU Short Range Shooting: 50
CPU Medium Range Shooting: 50
CPU Long Range Shooting: 50
CPU Dunk Percentage: 50
CPU Lay-up Percentage: 50
CPU Adjusted Shot Percentage: 50
CPU Adjusted Shot Frequency: 50
CPU On-ball Physical Defense: 33
CPU Poor Release Shot Percent: 50
CPU Double-team Effectiveness: 50
CPU Pro Hop Effectiveness: 50
CPU Drop Step Effectiveness: 50