ARLINGTON, Texas - The December trends hold: Philip Rivers and the San Diego Chargers are perfect, while Tony Romo and the Dallas Cowboys are perfectly miserable in the most important month of the regular season.

Rivers broke a fourth-quarter tie with a 14-yard touchdown pass to Antonio Gates, then followed with a drive that ate up more than 7 minutes and ended in a field goal, giving San Diego a 20-17 victory Sunday that keeps the Chargers rolling and the Cowboys reeling with the playoffs approaching.

San Diego (10-3) won its eighth straight and are on the verge of clinching the AFC West. The Chargers are 16-0 in December since Rivers became their starting quarterback.

"You don't want to fade out in December, you want to be peaking," said Rivers (21-for-32, 272 yards). "We've been able to do that the past few years. We just hadn't sustained it into January. Hopefully this will be the year we keep this thing going into 2010."

San Diego's last 11 December wins have come under Norv Turner, whom Cowboys owner Jerry Jones decided not to hire last time his head-coaching job was available. Jones picked Wade Phillips instead and hasn't gotten his money's worth in December: 3-8 after this loss; he's lost a total of seven games over three Septembers, Octobers and Novembers.

Players talked all week about wanting to win to boost Phillips' job security, but they kept failing during pivotal moments on offense and defense.

Now the Cowboys (8-5) are stuck with consecutive losses for the first time this season, and are headed to New Orleans to face the undefeated Saints on Saturday night. They also might be without star linebacker DeMarcus Ware, who was taken to a hospital after spraining his neck during the fourth quarter.

"Even though it might not look like we're playing the best football, you can turn that around in a hurry," said Romo (19-for-30, 249 yards). "I suspect this football team will do that."

Although this game was decided late, it tilted in San Diego's favor in the first half, when the Chargers held the Cowboys to a single field goal over drives that featured first downs 16, 3 and 27 yards from the end zone.

Dallas' first good scoring chance ended with a field goal that put it ahead 3-0. On the next deep drive, Marion Barber got to the 1 on first down, then was stuffed on three straight runs. The Cowboys moved him from fullback to halfback on the fourth-down play, but it didn't fool anyone.

"He's not getting paid to block," said linebacker Tim Dobbins, who was in on all three tackles from the 1. "We knew it was going to be a flip or a dive. I don't even know what they were thinking. I don't know if they watch film or what."

Throwing from his end zone, Rivers was intercepted, giving Dallas another short field. They wasted it when Folk missed a 42-yarder, making it five straight games with a miss. He's missed more kicks this season than his first 2 years combined.

"You've got make a certain percentage; he's not making that percentage," Phillips said.

Dallas ended up tying it at 10-10 on the final play of the third quarter, with Romo capping a 99-yard drive with a 6-yard touchdown pass to Miles Austin. Soon after, play was halted for several minutes because Ware was sprawled on the turf after ramming the crown of his helmet full-speed into the leg of a San Diego lineman.

Forced into third-and-12 from his 47, Rivers responded with a 39-yard pass to Vincent Jackson, then the go-ahead touchdown pass to Gates on the next snap.

After Romo failed to answer, the Chargers iced the victory by using up 7:17 on a 15-play drive that ended with a 34-yard field goal by Nate Kaeding. LaDainian Tomlinson had nine of his 21 carries, and 27 of his 50 yards on that series.

"There's nothing more gratifying than to do it like that," Tomlinson said.

Trailing by 10 with 1:56 left, Romo managed to get a touchdown - but it came with 2 seconds left. Then Gates caught an onside kick attempt, preventing a last-gasp chance from Dallas.

"This is a bitter pill to swallow," Jones said.

Jackson caught seven passes for 120 yards, and Gates had 44 yards receiving to go over 1,000 for the second time in his career.

Tomlinson ran for his 10th touchdown this season, his NFL-record-extending ninth straight year he's hit that plateau. It came in only the second game in Dallas for the Waco native who went to college at TCU in Fort Worth.