Is an 'Impact Substitute'???

Almost every footy match i watch on telly nowadays, i hear the commentator refer to a player as an 'impact substitute'....WTF?

Is this just the latest buzz word (s) doing the rounds in live footy television land, in the same way that the phrase 'a big ask' reared its ugly head?

Oh, and 'calmness personified' is another phrase you're guaranteed to hear

"Impact player" means someone who's brilliant for 10 minutes then burns himself out so he can't be used before the 80th minute, at which point you light the blue touch paper and stand clear.

"Calmness personified" is calmness that has acquired a persona so you can call it Mr, Mrs, Miss, Ms, Dr, Professor, or Master Calmness.