Chargers’ defense picks up Philip Rivers and paves the way for his record-setting day

On a day when Philip Rivers set a record for consecutive completions, he did fumble one opportunity — literally.

Behind 10-7, the Chargers quarterback turned the ball over in the second quarter and the Arizona Cardinals were set up for another score at the Chargers’ 35.

Arizona already had driven for scores on its first two possessions, and the Chargers’ defense could have teetered under the early work load. Instead it stiffened, and the Cardinals missed a 46-yard field goal.

When Rivers threw a touchdown pass five plays later, the Chargers went in front to stay en route to a 45-10 win Sunday.

But the defense had turned the tide.

“That was huge for our team,” coach Anthony Lynn said. “The momentum right there, it just shifted on our sideline.”

And it never shifted back, with Derwin James intercepting a Josh Rosen pass on the first play of Arizona’s next possession. That led to another Chargers touchdown … and the rout was on.

Arizona finished with just 149 yards of offense, the fewest the Chargers have allowed in eight seasons.

The Chargers gained more than that in the second quarter.

“It says a lot that we started [behind] 10-0, came back, took control and dominated for the rest of the game,” said defensive end Joey Bosa, who had two sacks, one in each half, in his second game of the season.

Rosen said the key for the Cardinals was to keep third down manageable. On their first two drives, they converted a pair of short third-down opportunities.

They converted just two others the rest of the way.

“They started making plays and we didn’t,” said Rosen, the former UCLA quarterback from Manhattan Beach who was playing his first game as a pro in Southern California. “I threw a pretty easy pick there which I shouldn’t have, obviously, and we just couldn’t go anywhere from there.

“It’s just a really good football team. There’s only so much you can do in third and long. The key is to have success early on and we stopped doing that.”

For Arizona coach Steve Wilks, it was more a case of the Chargers simply not allowing that.

“You’ve got to give those guys credit,” he said. “You look at [Melvin] Ingram, you look at Bosa — two premiere pass rushers in the National Football League. Those guys did a good job up front.”

Bosa had been sidelined since August by a left foot injury. He played 31 snaps in his season debut in last week’s loss to Denver and made more progress Sunday, recording his first sack to kill a a drive in the second quarter and force Arizona’s first punt.

“It felt amazing,” Bosa said. “It was excitement. We said, ‘We need a third and long here.’ We got the third and long, came out and got the sack. We kind of called the whole sequence.”

The turnaround by the defense also turned around the scoreboard, the Chargers transforming a three-point deficit into a 21-10 lead in just seven minutes.

“You have to score off turnovers. That speaks for itself,” Rosen said. “We went through a couple plays of basically giving them the ball exactly back where it was.”

An even bigger test for the Chargers will come next week when they travel to Pittsburgh to face a Steelers offense that ranks among the league’s best. And Bosa will be testing his foot in lower temperatures and potentially in precipitation.

“We all know what the Steelers are and what they can do. It’s going to be our toughest challenge in a while,” said Bosa, who added the Chargers can’t afford to get complacent after Sunday’s dominating performance.

“We were getting a little comfortable with ourselves last week,” he said. “These wins don’t come easy. Doesn’t matter who you’re playing against. So it’s about staying humble, knowing where we were a few years ago. Keep that same hunger, and stay a little salty.”

kevin.baxter@latimes.com | Twitter: @kbaxter11