Geno Smith thought he deserved to be drafted No. 1 overall. He was drafted 39th. Thanks to the rookie wage scale, that difference is in the millions of dollars. So he's fired his agents.
Per the Daily News, Smith has parted ways with the Select Sports Group, and according to the paper's sources, it's absolutely due to Smith's dissatisfaction with how the draft went. (For what it's worth, Smith denies it has anything to do with the draft.)
With the caveat that we have no idea what Smith's specific beef is, there are plenty of valid reasons for a recently drafted player to be upset with his agency. An agent gets a player ready for the combine; that means providing a training facility and program, and prepping him for his team interviews. Maybe Smith felt he wasn't properly prepared.
An agent acts as a player's pre-draft PR machine, hyping him to GMs and media, through means both above-board (phone calls, interviews, highlight reels) and nefarious (a good proportion of "Team X is high on Player Y" chatter comes from Player Y's agent). Maybe Smith felt he wasn't properly sold.
An agent prepares a player for the best and worst on draft night. While no one realistically thought Smith was going No. 1, the consensus was that he'd at least go in the first round. Instead, he dropped. He had to watch E.J. Manuel go ahead of him. We got to watch him sitting forlornly in the green room. He quietly slipped out of the building before the night was over. It was crushing, and until and unless he succeeds as a pro, that'll be most fans' lasting image of Geno Smith. Maybe Smith felt he wasn't properly warned—that his agents gave him assurances that didn't pan out.
Since the introduction of the wage scale there's almost no actual contract negotiations to handle, yet nearly every prospect hires representation the moment they declare. The story of Matt Elam, the only top prospect not to hire an agent, is a good look at what an agent can and can't help a player do before draft day. How important is this stuff? It's debatable. But it's important enough to Geno Smith, and that's what matters—it's his three percent he's shelling out.