Just a totally random thought I had, it's not tested or even very well thought out, but anyways...
How about bribing opposition players to perform, erm, not at their best? I think it could be an inducement, and the cost would be equal to the player's total value (ie base cost to hire plus any value modifiers for skills learned/stat increases). You can bribe as many players as many times as you have the cash, but each bribe must be given to a specific player on the opposing team.
Bribes can be used at any time to cause a player to "fail" any dice roll. eg, fail a dodge roll, or a roll to pick up the ball, or a pass, etc. The roll is automatically a failure (but not a fumble, in the case of a pass or similar). Bribes can also be used on block dice, in which case the player takes a dive and the block is automatically a result of Attacker Down, however, because even the most mercenary of players cannot be bribed to cause himself an injury, he is merely place prone - do not make any armour or injury rolls.
Note that bribes cannot be used on armour or injury rolls, since these are made by the opposing coach.
