Raiders’ Mario Edwards to likely miss first 6 games

Mario Edwards Jr. has been effective while on the field — but he’s had trouble staying there in his still-brief NFL career. Mario Edwards Jr. has been effective while on the field — but he’s had trouble staying there in his still-brief NFL career. Photo: Michael Zito, Associated Press Photo: Michael Zito, Associated Press Image 1 of / 7 Caption Close Raiders’ Mario Edwards to likely miss first 6 games 1 / 7 Back to Gallery

The Raiders might need to place defensive end Mario Edwards Jr. on the injured reserve list with a strained hip later this week, head coach Jack Del Rio told The Chronicle on Wednesday. Edwards would miss at least the first six weeks of the season.

Edwards was carted off the field after being injured in the Aug. 12 preseason opener at Arizona. At the time, team officials were relieved that the injury wasn’t more serious and said he might return in 4-6 weeks.

Now, the Raiders are deciding whether to take advantage of the extra roster spot that the IR list provides.

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Edwards could be put on inured reserve after the roster is trimmed to 53 players Saturday. At that time, the Raiders can make the designation and fill his spot. After six games, the team would have three weeks to decide whether he would return to the practice field as part of the 53-man roster.

(The old IR-designated for return list was eliminated this year. Now, teams can choose one player who has been on injured reserve for at least six weeks and activate him to practice.)

Edwards has had some bad luck in an otherwise bright start to his career. As a rookie, he played well at both defensive end and tackle before going down with a mysterious neck injury that cost him the last three games of the season.

Edwards wore a neck brace for a month and there was some concern that the sprained neck injury could threaten his career. But doctors said the weak neck was something he was born with and he could play again after doing neck-strengthening exercises.

Edwards was cleared in May and was eased back into his role during Oakland’s offseason workouts. He then missed a few days at training camp after injuring his hand in a practice fight with offensive lineman Kelechi Osemele.

When healthy, the plan is to move Edwards around even more on the front line. The 6-foot-3, 280-pounder had 2½ sacks and was stout against the run in 10 starts last season.

“I’m playing a lot of positions,” Edwards said during camp. “More than I am used to. Playing up, and down with my hand in the dirt. It’s good, really good.”

Luckily for Del Rio and defensive coordinator Ken Norton. Jr., the Raiders’ depth on the defensive line is also good.

Second-round draft pick Jihad Ward moved from tackle to end in Saturday’s preseason game against Tennessee. Denico Autry played well last season, but is still trying to get his bearings after offseason wrist surgery. He struggled against the Titans.

Putting Edwards on IR will remove the defensive-line drama from this weekend’s cuts. Two undrafted free agents, defensive tackle Darius Latham and defensive end/linebacker James Cowser, would appear to be locks to make the team along with fourth-year tackle Stacy McGee.

Edwards’ injury has put more pressure on defensive tackles Dan Williams and Justin “Jelly” Ellis to play well, and Del Rio said he thinks they’re ready to plug some holes in the Sept. 11 season opener in New Orleans.

“Big guys, big powerful guys,” Del Rio said. “Dan has come along slower than Jelly has. I think Jelly has really had a really strong camp, done a really nice job throughout, and Dan is coming on strong at the end here.”

Ellis is 335 pounds and Williams had him beat, but has worked hard to slim down a little since the offseason workouts.

“Raider Nation, they’ve been tweeting me and saying I’m fat,” Williams told reporters. He added that he passed the team’s conditioning test last month.

Vic Tafur is a San Francisco Chronicle staff writer. Email: vtafur@sfchronicle.com Twitter: @VicTafur