So this is how perhaps the greatest dynasty in modern professional sports ends, not in a moment of glory, but with the faintest of forced surrenders.

His jersey and his mouth hanging open, the customary silver chain dangling from his chest, Lance Armstrong’s Tour de France career came to an effective end with the Texan apparently holding back — of all people — Chris Horner, his teammate who missed last year’s race because of Astana’s persistent infighting. It appeared for large portions of Armstrong’s slow, painful, televised pre-retirement on the way to Morzine as if perhaps the Tour’s greatest rider was actually holding Horner back, a cruel image for the only man ever to win the Tour seven times, much less consecutively.

Of course, Armstrong’s career always had a (presumed) finite end. After coming out of retirement for last year’s Tour, the 38-year-old announced via his popular Twitter account that this go-round would be his last. Given his age and changed demeanor — Armstrong has, over the last two years, seemed far less combative and competitive than in his prime — it’s easy to believe 2010 will be it.

The cards were stacked against him, sure. Even given the strength of his Radio Shack squad, this year’s Tour is the deepest in years, likely richer with overall talent than any Armstrong had ridden previously. Contador, Schleck, Evans, Wiggins, even Leipeheimer — the names roll off like an all-star team.

Now, they roll on without their most high-profile compatriot.

“When it rains it pours I guess,” he said in via Twitter. “Today was not my day, needless to say. Quite banged but gonna hang in here and enjoy my last 2 weeks.”

Armstrong was the first to admit after the stage that so many times, the breaks, as it were, had fallen in his favor. Untimely crashes missed him by a whisker, teammates seemed to turn up at the right time. He once even took a ride through a country field and arrived further down the course after being forced off the road.

The cycling gods had been kind. Until last week.

It began after a very solid prologue saw Armstrong slotted in fourth. He rode well, but flatted over the cobbles on stage three and lost time. And then today, a series of crashes and mishaps involving or right in front of him caused him to lose his rhythm and, eventually, contact with his main rivals.

Levi Leipheimer, very much Armstrong’s right-hand man over the last two years, now appears Radio Shack’s de facto leader, though Andreas Kloden surely lingers as well.

“I thought he would really be up there in the front today, just all this bad luck for him,” Andy Schleck told reporters after today’s stage. “I feel little bit sorry for him. I know he wanted to be good in his last Tour. I think his morale is really low. I think he will try to win a stage.”

Armstrong himself admitted his Tour was over after he clocked in at nearly 12 minutes back. He openly pledged to ride for his teammates, hoping perhaps for a stage win and to enjoy his last two weeks as a rider in the Tour de France.

It’s a small irony that some in Astana’s camp felt Armstrong almost became better last year after Contador was the clearly established team leader. Suddenly, Lance was the veteran quarterback, calling out instructions and advice garnered over a long, impressive Tour career. Stage by stage, he helped guide Astana to Paris, and if not for Contador’s well-documented *ahem* individual decisions late in the race, the baby blue’s might have swept the podium in Paris altogether.

Radio Shack must hope he can recover from his road wounds and muster enough morale to become that steadying presence again. It seems likely — Armstrong is nothing if not deathly loyal.

And perhaps it’s a good way for such an impressive career to end, a reminder that, no matter what race we ride, fate (or karma, or whatever you would call it) catches up with us all. Sometimes, it’s just so damn cruel.