Oakland cornerback DJ Hayden was a feel-good story coming into the season, but the story is losing some of its luster.

The Raiders took Hayden No. 12 overall and said they would have taken him at No. 3, had they not been able to trade down. They liked him so much that they were willing to roll the dice, because coming to training camp, Hayden was still recovering from a near-fatal injury, a torn heart valve sustained in practice his senior season at Houston.

Good news: Hayden has been healthy, with seemingly no aftereffects of the injury. Not-so-good news: He's struggling on the field.

Coming into the game, Hayden had allowed 13 completions in 17 passes thrown to his man, for 152 yards, plus a 24-yard pass-interference penalty. In Week 3, he missed six tackles against the Broncos.

In Sunday's 24-14 loss to Washington, Hayden gave up the go-ahead touchdown late in the third quarter, a 5-yard slant from Robert Griffin III to Pierre Garcon. It came on 3rd-and-3 at the Raiders' 5, and the middle had to be protected.

"You're a cornerback, you're a high draft pick, you're a target," Oakland cornerback Mike Jenkins said. "It's up to you to prove to everybody on the other team that you're worth it. He is a great cornerback and he's just young.

"You don't want to tell (Hayden) too much stuff to have him mentally messed up. So you keep the motivational speeches positive. You don't want him going into a slump. You want him to have tunnel vision."

Head coach Dennis Allen, who wasn't into sugarcoating anything after the game, said of Hayden's coverage of Garcon on the touchdown:

"He needs to get tighter, yes, he needs to get tighter. That's another of those learning experiences for him."

Scott Ostler is a San Francisco Chronicle columnist.