Power
Oh yeah, you have some power as a sports agent. Power to make the deal of a century for the athlete of a century. Power to bring the talent to a team that may just push it over the top and to a Superbowl, World Series, or NBA championship.
But as anyone will tell you, with power comes responsibility, and abusing your power over your athletes, your employees, or the other people you work with—team managers, coaches, owners, other agents—might eventually come back and bite you in the you-know-what.
For example, say you gain enough power through your stellar reputation as a good and fair negotiator, a person of honesty and integrity. It'd be very easy to abuse that power by getting a small team to acquire one of your athletes at a price that's way above that player's market value. If your athlete doesn't perform, gets hurt, or is otherwise unable to play, that could bring down the entire team.