Or, the player selects an agent, that agent "sells him" that he is the best FS in the league. That he should demand or expect top money. In the end it's in the agents best interest to get the most money he can get for the player because that determines the agents cut.
So why wouldn't an agent, like Parker, who plays hard ball, convince Byrd that he is the best FS and can get top money? Yea, Byrd picked the agent, but I'm sure Parker "sold him" on his abilities and how much money he's worth.