It depends. There's nothing that can be done when the player is not in your team, you'll have to give in to the agents demands (You can still modify the contract to more suit your needs, but still..).
However, if the player is in your team, then asking the players to fire their agents is a must. It helps a lot. Furthermore, if an agent gets fired by a player, you still won't have a negative relation with the agent, so it doesn't affect future transactions.
Most times, firing the agent ensures that wage demands are lowered, and you won't have to pay agent fees. Occasionally, however, the player tends to be a bigger *** than the agent, and sometimes there is no difference.
As for success in getting the player to fire his agent, it depends largely on the players relationship with you, and also his personality. But once you've won something at the club, and are reasonably famous, it becomes relatively easier to get a player to fire his agent.
