Raiders place 2nd-round S Obi Melifonwu on IR

ALAMEDA — The Oakland Raiders invested plenty of draft capital in boosting a secondary that allowed more big pass plays than any other NFL team a year ago.

Now that they have a chance to show off how those changes will improve the defense in the season opener on Sunday at Tennessee one of those players will be on the sideline recovering from an injury while the other’s status is unknown.

The Raiders placed second-round safety Obi Melifonwu on injured reserve on Tuesday, forcing him to miss at least the first eight weeks of the season with a leg injury.

Meanwhile, firstround cornerback Gareon Conley hasn’t taken part in a full practice since June because of a shin injury and is running out of time to get up to speed for the opener against the Titans.

Conley had his first limited practice last week and took part in a walkthrough Tuesday. He has three practices left before the opener.

Conley and coach Jack Del Rio were unavailable for comment.

The Raiders did get some good news in the injury front in the secondary when cornerback David Amerson was cleared to practice after sustaining a concussion in the third exhibition game.

With Conley’s long absence and Sean Smith’s struggles in the preseason and training camp, Amerson is the surest bet in what is otherwise a suspect secondary.

“Right now we’re really polishing things up and getting ready to go to war,” Amerson said. “Hopefully it’s to the standards we know it should be.”

The Raiders allowed an Nfl-worst 61 pass plays of at least 20 yards last season and made a focus this offseason on fixing those issues. They drafted Conley and Melifonwu and also brought on former Chargers defensive coordinator John Pagano as a defensive assistant tasked with improving the communication on the back end.

After some shaky moments in the preseason, Amerson is pleased with the progress he’s seen of late and hopes the defense won’t drag down quarterback Derek Carr and the highpowered offense.