Interesting stuff
"If the player does not leave the field from any point within 10 seconds, the incoming player must undergo a 60-second waiting period before entering the game at the next stoppage. During the waiting period and prior to the entry of the substitute, the team shall play a man down. Exceptions to the rule include injuries and goalkeeper substitutions,"
"If a player with a suspected injury remains on the ground for more than 15 seconds, the referee shall stop play and send the medical team onto the field to evaluate the player. When it is safe, the player will be removed and remain off the field for a minimum of two minutes for further evaluation and treatment,"
trying to curb the time wasting and "injuries" that pop up from know where.