Straight from the manual:
A player with high stamina will tire more slowly, and can be effective for longer periods on the court.
Therefore, I'd say it's more important for players you use more often. Almost every player seems to have a higher rating when he's used as backup or for lower minutes during a game. So, for example, if a player only plays 10-15 minutes, he probably won't tire that much even if his stamina is inept. A starter who plays big minutes should have a significantly higher stamina if you want him to be effective though.
Additionally, the manual says:
Stamina is very useful especially if your team likes to use a fast paced offense.
...so if your player's stamina is low you might want to look into one of the slower paced offenses.
Last edited by Dunkface at 5/6/2011 10:00:02 PM