Page 33 of the Exhibition & League Rulebook covers a great example under Resilient. A Fury butcher with Savagery and a Gruesomes butcher with Resilient may sacrifice cards back and forth to increase or decrease the injury tokens (aka: adding or subtracting knives)
If the attacker does not have enough knives to beat the defenders toughness there is no injury, so no slaughterbox and no points for a "prevented" injury but since a knockdown still occurs the attacker still scores at least one point (unless the defender is a razor of course).
If the defender still had to go to the slaughterbox than purchasing Resilient for 100,000 would be a major ripoff! One of the counters for the slow movement of the Gruesomes is that you will probably still have the majority of your athletes in the pit at the end of the game. They truly shine in League play since they won't have to worry about lasting injuries like other teams.