With the win, San Diego claimed its eighth victory in a row while the Cowboys continued their trend of disappointing Decembers losing their second in a row this month.
And it doesn't get any easier from here on out as Dallas travels to undefeated New Orleans next weekend before facing NFC East rivals Washington and Philadelphia.
In addition, Dallas could be without the services of Pro Bowl linebacker DeMarcus Ware, who was carted off the field on a stretcher in the fourth quarter after suffering a neck sprain.
Cowboys officials said after the game that Ware was "aware and alert with full movement and strength in his extremities" when he was taken off the field.
He was then taken to a local hospital for X-rays and further evaluation.
"There's no one more disappointed then I am that we didn't win those games and that I didn't do a good enough job to help win those games," head coach Wade Phillips said afterwards. "But the season is not over and we are going to go in with the same attitude we had and hopefully a little better."
Dallas had its chances in the first half, even though San Diego's defense was stout as any unit seen all season by the silver and blue.
Leading 3-0, Marion Barber setup first and goal at the one-yard line before he was stopped on three consecutive runs. The Cowboys moved him from fullback to halfback on a fourth-down play, but once again he was stuffed for no gain.
"We felt like we were strong enough to make it down there and I felt like if we didn't make it we would at least have them backed up and have another chance to score before the half because they were getting the ball back the second half and it turned out we ended up getting another interception and did have a opportunity," Phillips said.
"But they stopped us two downs very close to the goal line. That was disappointing for all of us."
Wide receiver Roy Williams also offered an explanation of his own regarding the sequence and the game itself.
"You can't blame it on that one drive," he said. "I don't know how many possessions we had. We had opportunities. We like to score… but they play defense to.
"I think we ran the ball pretty good. Ninety-nine yards worth. I don't even know if we threw a pass on that drive. But it was a good game. I have never been to the playoffs but that seemed like a playoff game to me, atmosphere wise."
The Dallas defense would hold after the turnover on downs, forcing a rare Rivers interception, however the opportunity was wasted after Nick Folk missed another makeable field goal from 42-yards out.
Folk has now missed more field goals this year than his first two years in the NFL combined.
"Certainly you are not going to make them all, but you need to make a certain percentage and he is not hitting that percentage rate right now. We changed holders, we hoped that would go through and didn't," Phillips said of his former Pro Bowl kicker.
San Diego would take a quick 10-3 lead after a LaDainian Tomlinson one-yard touchdown run and a Nick Kaeding 29-yard field goal in the second quarter.
The Cowboys would counter with a 99-yard touchdown drive to tie it at 10 on the final play of the third quarter before Gates' 14-yard touchdown reception put San Diego ahead for good.
Romo finished the game 19-of-30 for 249 yards and two touchdowns, and no interceptions but he was outplayed by Rivers, who was 21-of-32 for 272 yards and a touchdown.
"We have to come back and fight on Tuesday and prepare for New Orleans," cornerback Terence Newman said. "The season isn't over; we can still do what we want to do. We just have to go out and do it.
"Everybody keeps talking about December, but they lose focus of the biggest picture. It's not about winning games in December; it's about getting to the playoffs and winning it."
NOTES: Tony Romo now has three straight games without throwing an interception – tying the longest streak of his career set earlier this season. ... Jason Witten's four catches today upped his career total to 506 and allowed him to pass Frank Wycheck (505) for fifth in league history among tight ends.
December woes continue
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