Here's an excerpt from the BRD to show how difficult life has become.

SUBSTITUTES: ILLEGAL

FED: DEFINITION: An illegal substitute is:

(1) a player who is ineligible to participate, which includes a withdrawn substitute, a twice-withdrawn starter, and ejected or restricted players (3.1.1c); or

(2) any player, including the player for whom the DH is hitting, who reenters in the wrong spot in the batting order; or

(3) a designated hitter who enters the game on defense while the player for whom he is batting is still playing defense; or

(4) a courtesy runner who violates the courtesy-runner rule. (2-36-3) 

Continued...