Chargers offense finds rhythm with Rivers back in the lineup

Philip Rivers opened up the Chargers’ preseason with a methodical touchdown drive against the Seattle Seahawks. Then, he went to the bench.

He stayed there for the next 25 possessions, a stretch that lasted the rest of the opener and all of the team’s second preseason game. Without him, the Chargers scored 10 total points and went 18 straight drives without a score.

But it’s probably not a coincidence that the offensive struggles that began with Rivers heading to the bench magically ended when he came off of it Saturday night at the Coliseum.

Rivers led the Chargers on two touchdown drives on the two series he played, completing all six of his passes, in his team’s 21-19 win over the Rams.

Over the course of the 15 plays he was on the field, the Chargers moved down the field without much issue, snapping the ball on third down only twice.

On the first third down, Rivers sat in the pocket with plenty of time from his offensive line, before finding Travis Benjamin steps ahead of a pair of defenders for a 45-yard touchdown strike. It was Benjamin’s second long touchdown of the preseason.

Rivers’ second drive was more about Melvin Gordon than the veteran quarterback, with the Chargers finally getting their running attack going.

Gordon carried the ball six times on the drive, gaining 26 yards, including the two he needed to score the team’s second offensive touchdown. Gordon reliably picked up yards behind right guard Kenny Wiggins and right tackle Chris Hairston, who was starting in place of Joe Barksdale.

Keenan Allen continued his strong preseason by catching all five of Rivers’ targets.

In between Rivers’ two touchdown drives, the first-string defense made sure the spotlight Saturday night would be shared.

After the Rams moved down to the Chargers’ 11-yard line, defensive end Joey Bosa sacked and stripped Jared Goff, badly beating the Rams’ right tackle, Rob Havenstein. Melvin Ingram scooped up the loose football and sprinted 76 yards for the touchdown.

The next time the defense took the field, cornerback Jason Verrett, playing in live game action for the first time since tearing his ACL early last season, made an immediate impact. Verrett stepped in front of a quacking pass from Goff and picked it, setting up Gordon’s two-yard score.

Even without starters like tight end Antonio Gates, wide receiver Tyrell Williams and cornerback Casey Hayward, the Chargers’ starters built a dominant 21-0 lead.

If there were a flaw in the early performance, it came on the defensive side of the ball. The Chargers weren’t quite stingy enough against the Rams’ ground attack — even with Todd Gurley out as a healthy scratch.

In the first half, Rams backup running back Malcolm Brown averaged 4.9 yards on nine first-half carries. Coming into the game, the Chargers’ defense had allowed opponents 4.2 yards per rush.

But the Chargers’ depth again came into question, as the team failed to score with Rivers on the sideline and the defense allowed the Rams to kick their way back into the game.

The Rams kicked four field goals, three in the second quarter, while the Chargers offense failed to threaten without Rivers under center. Cardale Jones, who had been operating as the team’s No. 3 quarterback, replaced Rivers in the first quarter and looked sharp enough, minus an interception into tight coverage.

Jones completed nine of 13 passes for 74 yards, rushing for seven more.

The most promising Rivers-less drive came in the third quarter when completions to Geremy Davis and Sean Kulkin plus a 13-yard run from rookie Austin Ekeler had the team across midfield. But running back Andre Williams, who is competing for a spot on the roster, fumbled.

The back-up defense gave up a touchdown in the third quarter when cornerback Randall Evans was beaten on a 38-yard reception.

The Chargers will have one more game to figure out ways to score without Rivers on the field Thursday against the 49ers in San Francisco, where the team will close out the preseason with most of its regulars on the bench.

dan.woike@latimes.com

Twitter: @DanWoikeSports