Raiders coach Jon Gruden knows Philip Rivers always keeps Chargers in running

Philip Rivers is off to such a notable start that it was even big news Sunday when he rushed for one yard.

The Chargers, who hadn’t run a quarterback sneak with Rivers since 2011, had the 36-year-old convert a fourth-and-one in the first quarter against San Francisco.

“Just because nobody was expecting that,” offensive coordinator Ken Whisenhunt said, “we thought it might have a chance.”

Through four games, the offense has gained 1,655 total yards. But those other 1,654 weren’t nearly as historic as Rivers’ one-yard keeper.

The Hall of Fame-bound quarterback also never has passed for more touchdowns through the first quarter of a season than the 11 Rivers has entering the Chargers game against Oakland on Sunday.

He has thrown just two interceptions and, thanks in part to his quick trigger, been sacked only five times. Arizona’s Sam Bradford, as one comparison, has been sacked six times with 67 fewer pass attempts.

“He’s fully committed,” Raiders coach Jon Gruden said. “He’s full metal jacket. He’s all in. His preparation behind the scenes is legendary, really.”

Rivers is in his 13th season as a starter but has faced a Gruden-coached team only once. In 2008, the Chargers beat Tampa Bay on a day when Rivers threw for four touchdowns.

He has defeated the Raiders 16 times in 24 starts, his most accomplished record against any opponent.

So, even playing in front of a StubHub Center crowd that’s expected to be so pro-Raiders that the Chargers practiced this week amid blaring, artificial crowd noise, Rivers figures to be comfortable.

“They’ve had different defenses and different coaches and things over the last 15 years,” Rivers said, when asked about his success against Oakland. “So I don’t think there’s anything to a certain scheme or anything like that. But hopefully we keep it going.”

In the 24 games against the Raiders, Rivers has completed 64% of his passes for 6,055 yards, with 41 touchdowns and 18 interceptions.

This time, he’ll face a defense that is next to last in the NFL in points allowed and just permitted Cleveland and its rookie quarterback Baker Mayfield to score 42.

“He’s still as talented as he has been in the past,” Gruden said of Rivers, who, since Week 11 of last season, leads the NFL in passing yards and touchdowns. “His legs are in great shape. They have a creative scheme and a lot of problem weapons to deal with.”

And now the Chargers have Rivers’ feet as a weapon as well, although one yard at a time isn’t likely to be enough on an NFL Sunday.

Hurt locker

Left tackle Russell Okung (groin) was again limited in practice Friday, with the Chargers officially designating him as questionable against the Raiders. Coach Anthony Lynn said a decision on Okung’s playing status would be made Sunday.

Right tackle Joe Barksdale (knee) also was limited in practice and is listed as doubtful.

Wide receiver Travis Benjamin (foot) did not practice and isn’t likely to return until near the end of the month. His right foot is in a cast and Lynn said the plan was for Benjamin to rest the injury for “a couple weeks.”

Liuget is back

The Chargers expect to have defensive tackle Corey Liuget back Sunday after he served a four-game suspension for testing positive for performance-enhancing drugs.

“For my own sanity, just to get out there and play, I think would be great for me,” Liuget said. “Just get these jitterbugs off of me.”

Liuget’s return figures to help the Chargers’ defense against the run. Lynn said the presence of the 6-foot-2, 300-pound Liuget might even aid the pass rush, which has been lacking.

“He’ll help defend the run,” Lynn said. “Getting a little push in the middle … it might take some pressure off the outside pass rushers.”

jeff.miller@latimes.com

Twitter: @JeffMillerLAT