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 today, 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 also are 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.