PATRICK HERTZOG / AFP/Getty Images

Lance Armstrong rides ahead of Fabian Cancellara and Andy Schleck during the 17th stage.

updated 2:30 p.m. ET July 22, 2009

LE-GRAND-BORNAND, France - Lance Armstrong couldn’t stay in the front during the final Alpine stage in the Tour de France, so he played faithful teammate for Alberto Contador instead.

When all was said and done in Wednesday’s Stage 17, the 26-year-old Spaniard further cemented his grip on the yellow jersey and Armstrong’s ambitions for a podium spot were dealt a setback.

Frank Schleck and his younger brother Andy bumped the Texan down to fourth place from second as they broke away with Contador at the end of the 105-mile stage. The elder Schleck won the stage.

Contador leads his closest challenger — Andy Schleck — by 2 minutes, 26 seconds, and seemingly only a major mishap could stop him from taking home the yellow shirt when the race ends Sunday.

Armstrong’s challenge for a spot on the podium on the Champs-Elysees rides on the question: Can he regain ground in the time-trial Thursday, and then hold on Saturday on the dreaded Mont Ventoux?

He says a second-place finish is still within his reach.

“Yes, it’s still my goal, I think it’s possible,” Armstrong said. “I just need to work hard on the time-trial tomorrow... We still have two big days.”

Frank Schleck is 3:25 behind Contador. Armstrong, who crossed the finish 2:18 after the leading trio, now trails by 3:55 — ending any hope that he will win the Tour, barring a miracle.

And Astana’s hopes of sweeping the final podium in Paris are also in trouble after another Contador attack, this time on the toughest mountain stage in this Tour, with five punishing ascents in succession.

The drama set in during the super-steep Colombiere pass.

When the 2007 Tour champion, teammate Andreas Kloeden and the Schlecks were alone in front on the Colombiere, the Spaniard surprisingly mounted his own attack on the two brothers, who had tried all day to shake the Spaniard.

Contador, too, couldn’t get rid of the Schlecks and instead dropped his teammate Kloeden, who lost significant time to the brothers and dropped to fifth overall. Kloeden started the day in fourth, trailing Contador by 2:17. At day’s end, he was 4:44 back from the leader and 1:19 behind third-place Frank Schleck.

The attack prompted much discussion after the stage.

Armstrong tweeted: “Getting lots of question why (Alberto Contador) attacked and dropped Kloeden. I still haven’t figured it out either. Oh well.”

Contador said he discussed attacking the Schlecks with team manager Johan Bruyneel by radio, who then advised him to take it up with Kloeden.

“He told me, ’Go for it,”’ Contador said later. “Andreas told me that he could attack without problem — but then the Schleck brothers surprised me a lot, and when I saw that it would be hard for me to make a gap I stopped.

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Earlier in the stage, Armstrong worked on Contador’s behalf to help him gain time on Bradley Wiggins, a time-trial specialist. Wiggins began the day in third overall, 1:46 behind the Spaniard and only 9 seconds back of Armstrong.

On the Colombiere, Armstrong couldn’t keep up when Contador got out front with Kloeden, and the Schlecks, both on the Saxo Bank team.

Instead, Armstrong stayed back alongside Wiggins to protect Contador. Had the Texan accelerated right away, it might have allowed Wiggins to close the gap behind Contador.