This is why you keep watching.

Out of nowhere, out of a Washington losing streak that threatened to turn the rest of this season to ashes and dust, the Redskins and Cowboys played one of the more entertaining games in their long rivalry Sunday.

Why do these two teams care so much the instant they see the opposite uniform? Why do they dislike each other so much and raise their intensity to a level usually associated with January?

Who knows, but it happened again.

A game billed as boring turned out to be an overtime thriller. A Redskins team assumed to be deceased acted like it hadn’t received its death certificate yet. A contending Dallas team coming off a 37-point win and feeling, perhaps, a bit too good about itself, blew a 10-0 lead and watched the Redskins score with 14 seconds to play to force overtime. Then, the ’Boys watched helplessly as a 52-yard field goal attempt by the Redskins’ Graham Gano slid wide to the right early in the extra period.

With the Redskins now 3-7 after six straight defeats, and more injuries arriving every week, this 27-24 loss will eventually blend into what will probably be remembered as a gray season of rebuilding and slow learning.

But this game, this one balmy fall afternoon, truly gleamed with passion. Some games show the worst in a sport or its players. This battle showed a fair slice of what’s best in the NFL and in the tough and fanatically committed men who play in it. All that talk about playing for pride, about learning to despise a team you face twice a year and about wanting to play your best for your fans — it’s not always just talk.

For the last three weeks, the Redskins could hardly have been a more dismal team to watch. They knew it. They showed up Sunday anyway. Perhaps best of all, when everyone wanted to congratulate them on their effort afterward, they were too disgusted to accept any of it.

“I’d rather talk about silver linings on Wednesday,” quarterback Rex Grossman said.

That bitter taste stays in the mouth because pros know what it actually feels like — the risk, the pain, the injury — to play in a game that starts off like a routine boxing match, then suddenly turns personal, and finally evolves into a brawl with everything in play except the ring stools.

Afterward, linebacker London Fletcher wore a shin-high boot on his sprained ankle. He hurt it last week, then played — spectacularly — through the pain all afternoon. Think about this stat line for “a hobbled man,” as Fletcher called himself: 16 tackles, including two for losses, and a 12-yard sack, a forced fumble and another quarterback hit.

“You play for those moments. I’m disappointed we didn’t get a victory. But I enjoyed myself in that Redskins-Cowboys rivalry game,” said Grossman whose numbers were almost identical to Dallas quarterback Tony Romo’s — 25 for 38 for 289 yards, two touchdowns, an interception and a four-yard touchdown run on a quarterback draw.

“Fighting [beside] my teammates, the support from the fans. . . . It was a very interesting time. . . . This rivalry, it is the best in the NFL. Extremely, extremely disappointed, but we fought our [butts] off.”

The nasty numbers say that, out of more than 40 active quarterbacks with extensive playing time, Grossman ranks last or next to last in the career stats that matter most, including worst interception percentage and worst quarterback rating. His mistakes are ugly, his decisions sometimes mysterious and, on Sunday, only a replay reversal prevented him from being charged with a fumble that Dallas scooped and returned to inside the Washington 1-yard line. If Grossman’s knee hadn’t been ruled down, barely, this game might have been 17-0 in the first quarter and ended in a Train Rex rout.

But his teammates enjoy battling with him. He has moxie, cockiness — sometimes too much, but at least if you were in a bar and heard the first beer bottle bust, Rex would probably be looking for a pool cue to cover your back. Not that any such circumstance would ever befall a pro football player. Sure, you want somebody better, ASAP. But you can root for a guy who never seems to notice he’s screwed up again, been knocked down or counted out.

Grossman even spotted ex-Redskin Doc Walker, supposedly now in the media, cheering for him like mad on the sideline because . . . well . . . because a real Redskins-Cowboys game had broken out. “It pumped me up,” Grossman said.

No matter what the Shanahans claim to think, Grossman isn’t going to be transformed into Joe Montana by their scheme. But if, or more likely when, he goes back to his turnover ways, at least remember the perfect touch pass, 23 yards up the left sideline to a diving David Anderson, that set up the first Redskins score, which came on Grossman’s own dive for the goal line.

Just before half, Grossman fired a bullet to Jabar Gaffney on a quick veteran double move that left him open, for an instant, in the back of the end zone, for a 14-10 Redskins lead. And that was also Grossman, on third and four with 14 seconds left, who lofted a perfect back-corner pass to wide receiver Donte Stallworth to produce overtime. Give credit: Grossman is working with spare parts, guys picked up off the street, kids and old pros.

Much of the previous five weeks have been so bleak that it’s easy to read too much into this one credible showing against a 6-4 Dallas team. But in a sport that routinely leaves men crippled at 50, you give high marks for efforts this estimable when they come deep into a season that seems lost.

Is the Redskins’ effort a result of new players who have been added or some of the old ones — no names, please — who are now long gone?

“It’s a combination of both,” said Fletcher. “It starts with [Mike] Shanahan. Sometimes you think, ‘Oh, this guy is more talented, but if he doesn’t fit what we’re trying to do, then he’s not the guy we want in the locker room.’ . . . When the situation is not going your way, you can have some guys go separate ways. That’s not the makeup of this football team.

“You saw the byproduct of that today with the way we fought.”

Fighting hard, showing up, moral victories — they all get old mighty fast. But compared to what the Redskins have been putting on display recently, such a game may have been a necessary step.

“We’ll go with the guys we’ve got,” said Gaffney, a 10th-year veteran who had to carry the load with seven catches for 115 yards because Santana Moss, Leonard Hankerson and other receivers are hurt. “We left it out on the field. We’ll be out and ready at practice this week. We’ll be ready when we go to Seattle [next Sunday]. We’ll come back with a win.”

They actually believe it. As long as they do, you can still watch.

More on Redskins vs. Cowboys

Ask Boswell: Discuss the Redskins’ loss and more at 11 a.m.

Jason Reid: Redskins may be losing, but they aren’t quitting

Graham Gano: ‘No excuses’ for missed field goal