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HOUSTON -- Philip Rivers picked apart the Houston Texans' porous pass defense, even without some of his favorite receivers.

The NFL's leading passer threw four touchdowns on Sunday, and the San Diego Chargers earned their first road win of the season in beating the Houston Texans 29-23.

The Chargers (4-5) were missing tight end Antonio Gates (torn plantar fascia) and wide receiver Malcom Floyd (hamstring) to injuries. They're also awaiting the return of Vincent Jackson, who signed his contract tender on Oct. 29 and has one game left on a team-imposed suspension.

Rivers didn't miss any of them on Sunday, using eight different receivers in completing 17 of 23 passes for 295 yards. Rookie Seyi Ajirotutu and backup tight end Randy McMichael caught two touchdowns apiece.

"I usually don't get to throw Tutu a ton of balls, or Randy for that matter, because practice reps are so valuable," he said. "If something is up for tight ends, Gates usually takes it. The last week or two, I was able to throw those guys a lot more balls than I have in the past and it certainly paid off."

The Chargers head into their bye week on their first two-game winning streak of the season.

Ajirotutu just moved up to the active roster on Oct. 23, when linebacker Kion Wilson went on injured reserve. The undrafted rookie out of Fresno State clutched the game ball in the locker room after catching four passes for 111 yards.

"I'm going to hold onto this for a while," he said. "I'll probably let it go after the bye week. I'm just glad I was able to get it. There was a lot of people that helped contribute to this win and I'm just glad I was able to get one."

Arian Foster rushed 27 times for 127 yards and two touchdowns for Houston (4-4), which has lost three of its past four home games.

"You've got to protect your home turf," Houston coach Gary Kubiak said. "Obviously, we haven't done that."

This time, Houston failed on two fourth down plays in the second half to blow a 23-14 lead.

McMichael's second TD catch cut the lead to 23-21 with 5:55 left in the third quarter, and the Chargers stuffed Foster on fourth-and-1 from the 17 early in the final quarter.

Rookie Kareem Jackson has taken much of the blame for the Texans' 32nd-ranked pass defense, but he intercepted Rivers' pass to Ajirotutu near midfield with about 12 minutes left.

Rivers atoned on the next possession, throwing over Jackson for a 28-yard touchdown pass to Ajirotutu with 5:23 left. Mike Tolbert jumped over the pile for a 2-point conversion to give San Diego a 29-23 lead.

Rivers said last week that the Texans' secondary was vulnerable to deep passes. When the Chargers tried big plays on Sunday, Rivers said they clicked as well as they did in practice.

"A couple of things came up just how we drew them up," he said.

Rivers has 2,944 yards passing this season.

"He can make any throw," San Diego coach Norv Turner said. "He understands what we're doing. He makes a lot of guys look like real good players, and we got some young guys that are going to be good players."

The Texans had a chance for the go-ahead score in the final minutes, but the usually sure-handed Andre Johnson made a costly mistake.

On second down, Johnson couldn't handle Matt Schaub's pass, and the ball ricocheted off his knee and into the hands of safety Paul Oliver. Officials upheld the interception after a replay review, and Rivers kneeled down to run out the clock.

"No matter what happened during the game before that play, we still had a chance to win that game," Johnson said. "I thought I had it. My knee came up, the ball hit off my knee, and the guy picked it off."

The Chargers improved to 4-0 against the Texans after starting the game with the kind of special teams blunders that have hurt them all season.

Oliver caught the opening kickoff and inexplicably stepped out of bounds at the San Diego 4. Texans linebacker Stanford Keglar then deflected Mike Scifres' punt, and Houston recovered at the Chargers 8.

It was the fifth San Diego punt blocked or deflected this season, and Foster scored on the next snap.

Ajirotutu then sprinted past Jackson on a 55-yard touchdown pass from Rivers, the eighth reception covering more than 40 yards this season against Houston's secondary.

Game notes

Rivers' other four-touchdown game came in a 41-24 win over Tampa Bay in December 2008. ... The Texans' defense faced a top-five offense for the fifth time this season. ... McMichael had the first two-touchdown game of his career. ... Foster scored multiple touchdowns for the fourth time this season.