Resting is all good when you have the playoff spot wrapped up. But that wasn't the case in the NL Central. All 3 teams had to push their best guys to the max. Starters are starters for a reason. Bench players are bench players for a reason. Few teams have 4-5 starting caliber players sitting on the bench. Same with pitchers.ARGH. "They get paid" is a terrible reason to run your guys into the ground. It is the job of the GM, coaches/manager, and training staff to have guys in peak condition come the playoffs. That means considering whether playing Yadi nearly the most games of any catcher in the NL is a good idea. That means evaluating skipping starts for certain SP. That means evaluating how you use your bullpen. That means telling guys no when they press to play every day. Etc.
The NBA is all over this - the good teams like San Antonio are resting their starters more and more (both in terms of missing games and lowering their minutes played per game) so they are fresher for the playoffs and are less likely to develop injuries caused by overexertion. The dumb teams like the Bulls run their guys into the ground so they get hurt and so they are dead come the playoffs.
I'd venture a guess that if the Spurs were fighting for a spot they wouldn't be resting their best guys so much.