I have discovered the True Tactic of preventing tired players in many games

[Siddharth Shanker Singh]

Indeed very true, but the OP was concerned with how tired the players are, and friendlies do tire players.

If you are only playing 2 competition then you can play friendlies on days when only 1 match scheduled...More ever you can also play friendlies by your lesser quality team(substitutes)......