Sitting Players to Manipulate Playoffs

Interesting situation in my league currently,

Team A - Win this week clinch playoffs Team B - Already clinched playoffs Team C - Needs to win this week AND team A to lose

So essentially team B is sitting their players this week so that team A automatically wins and clinches playoffs. Team B views Team A as weaker than Team C so they would rather have team A in the playoffs.

Would you allow this in your league?