HOUSTON -- The San Diego Chargers entered Sunday's game allowing 27.8 points per game, the fifth-worst average in the NFL.

Yet the Houston Texans could score only 13 points in a 21-13 loss to the Chargers.

After the Texans' passing game showed improvement last week against the Raiders, quarterback Brock Osweiler finished 22-of-36 for 246 yards and three interceptions against the Chargers. Osweiler's passer rating was 45.6. He also had a 1-yard rushing touchdown.

Osweiler’s three interceptions give him 13 on the season, 10 of which have come at NRG Stadium. The Texans' opponents have scored 34 points on the drives after intercepting Osweiler, seven of which came Sunday. Osweiler said he didn't see a consistent theme as to why he's throwing interceptions, but acknowledged that "it's happening too often."

At home this season, Houston’s running game has carried Osweiler and the passing game, but the Texans couldn’t get any of their offense going against the Chargers. San Diego’s fifth-ranked rushing defense held running back Lamar Miller to 57 yards on 19 carries. Miller also lost a fumble in the third quarter in Chargers territory. In Miller's previous five games, he had run for 453 yards, including 104 yards on Monday against the Raiders in Mexico City.

"We feel like we have a lot of talent on this offense," veteran tackle Duane Brown said. "We feel like we can put up points. We had opportunities to do that. Thirteen points is not enough."

One part of the passing game that has succeeded this season is when Osweiler throws to one of his three tight ends. But in Sunday's loss, tight ends C.J. Fiedorowicz, Ryan Griffin and Stephen Anderson combined for nine catches for 86 yards on 12 targets.

Pro Bowl receiver DeAndre Hopkins had five catches for 70 yards, and rookie receiver Will Fuller had four catches for 60 yards, his best game since Week 4. San Diego entered the game with the 27th-ranked pass defense, having allowed an average of 275 yards per game.

The Texans couldn't sustain drives, with only five drives of more than five plays. Houston was 4-of-11 on third down; the Texans had just 19 first downs in the game.

"Our job as an offensive unit is to score touchdowns and put together multiple drives that result in touchdowns every single week," Osweiler said. "And we've struggled with that this year. And I can't quite put my thumb on that but I will certainly always stand up and point the finger at myself. Bottom line, being the quarterback of this football team, having the ball in my hand every single play, I need to find a way for us to score touchdowns and certainly a lot more touchdowns moving forward."

Houston has scored three touchdowns in a game only once this season; Osweiler hasn’t thrown for more than two scores in a game.

The loss to the Chargers was the Texans' first home defeat this season, but the team was greeted with boos several times after offensive drives stalled, and NRG Stadium emptied out in the fourth quarter.

"Can't blame them," Brown said of the booing. "We've got to go out there and put a good product on the field. We didn't do that today. You have to give people something to cheer for."

Now at 6-5, the Texans will barely hold on to the AFC South lead they have held since the first week of the season. But Houston's offense has not shown it can help the Texans hold on to win the division for the second consecutive year.

"I know we've had some ups and we've had some downs and you'd like to see steady improvement, but sometimes that doesn't take place,” Osweiler said. “I'm very optimistic about what this team can accomplish because this is a damn good football team and I let them down today. I need to play better."