I don't agree.  I do what is best for my team. You are my enemy.   I owe you nothing.

I always look at the teams I'm playing. If they are out of the playoff race I rest the players that need it. If they are still in the hunt they face my normal lineup and pitchers. I would expect it to be played the same against me as well. Sportsmanship at its finest!

I tend to side with TJ on this one, and I've done more or less exactly the same thing myself.  If I have fatigued guys late in the season and have clinched a playoff spot, I don't think I'm at all obligated to continue to play them just because my opponents may be in a pennant race.

I'll point out that I also do this (rest a bunch of players at once, bat the pitcher leadoff) periodically throughout the season if I need to manage fatigue closely.  Mostly in interleague games, but not exclusively.  So it's rarely the case that only my last 1-2 opponents benefit from this.  They just happen to do so at the end of the season, when it's more clear whether or not the games matter.

Once my team has clinched a playoff spot my only priority is to have them as rested and ready as possible, anything else concerning the divisional races is immaterial.

I have to agree. I dont see this as a "sportsmanship" issue. A manager does what is best for HIS team..not someone elses. They have no obligation to help or hinder your playoff chances.

I'm just curious - have you ever been in a league where the shoe was on the other foot? When YOU beat a bunch of 200k guys and got a playoff spot out of it? Would you have complained about that too?

I am with TJ - my team is my concern. I won't maliciously rest guys who don't need to be rested. But if they need to be rested, you bet I will rest them.

We'll have to agree to disagree on this doubletruck.  I see no similarity between resting players (even to the extent that it tanks my team) and the other situations you describe.

No, I won't.  The point is, it's your choice. 

This sort of thing happens in the NFL every season more or less.

I also have no problem with players who lead in batting average (like Wilson vs Yount in 1982) or ERA sitting out the last day of the season.  They're not obligated to play.