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Lance Armstrong is battling teammate Alberto Contador for supremacy of Team Astana and possibly the Tour de France.

It's telling that the only three-week victory in which Contador grew stronger was the 2008 Giro d'Italia. That's the one that Astana was initially not invited to (along with that year's Tour). Contador, famously, hadn't trained for the race and was vacationing on a beach when he found out his team had been unexpectedly invited. In his book We Might as Well Win (which I co-wrote), Astana team director Johan Bruyneel says Contador at first refused to participate because he felt his fitness wasn't high enough.

Contador doesn't collapse — he's still a great champion, the best stage racer of his generation and an apparent legend in the making. But, at least in this point of his career, he doesn't respond as positively to the rigors of the final week as Armstrong does.

And this year's Tour has such an extreme final week that this slight difference between them will put Armstrong in yellow.

Stage 15 has four Category 3 climbs and one Category 2, plus a finish atop Verbier, a Category 1 mountain that ascends 8.8 km at an average grade of 7.5 percent. (In the Tour de France, climbs are ranked in difficulty from Category 4, the easiest, up to HC, or hors categorie, which is so hard that it is considered beyond categorization.)

After a rest day, the Tour goes over the HC col du Grand Saint-Bernard, drops for 35k, then ascends the 22.6-km, Category 1 col du Petit Saint-Bernard before plummeting 29k to the finish. On the 24.4-km Grand Saint-Bernard, four of the final 5 km hit an average slope of 9 to 9.5 percent. (For reference, that's the kind of steepness that within a block or two makes the general public get off their bikes and walk.)

Stage 17 has a Category 2 and four Category 1 climbs, of which the final two, col de Romme and col de la Colombiere are essentially combined into one long monster. Romme is only 8.8 km but starts off with kilometers of 9.8, 10.5 and 9.1 percent and averages 8.9 overall. The route drops just 5 km from Romme's crest before crashing into the 7.5-km Colombiere, whose final 10.2-percent kilometer is preceded by 3 km at 9 percent.

Then, at the end of the 167-kilometer Stage 20, comes Mont Ventoux. It rises 21.1 km at 7.6 percent, combines nasty stretches of 9- and 10-percent just after the start and in the middle, and finishes on an exposed, wind-swept, sun-baked lunar-like landscape whose final two kilometers average 9.5 percent.

Somewhere in there, Contador will falter and Armstrong won't. I'm going to guess that Stage 16 will be decisive, though the time gaps won't stop shifting until the riders stand atop Ventoux.

To be fair, there are others in the race, as well. Of the riders who could still be considered legitimate contenders, Garmin-Chipotle's Christian Vande Velde is 1:16 behind Armstrong; Saxo Bank's Andy Schleck is 1:41 down; Cervelo's Carlos Sastre is 2:44 back; and Silence-Lotto's Cadel Evans has 2:59 to make up. (The current owner of the yellow jersey, AG2R rider Rinaldo Nocentini, who leads the second-place Contador by six seconds, isn't a threat for the overall win.) With super-domestiques Leipheimer (who has finished third in the Tour) and Andreas Kloden (who's twice finished second), Astana probably has the firepower to contain those riders. If not, both Armstrong and Contador should be able to minimize any time losses in the 40.5-km time trial in Stage 18.

In addition, Armstrong is in uncertain territory this year. In his victorious Tours, he's never not been in yellow by the time three mountain stages passed. (Stage 9 was the third this year.) Of his seven Tour de France wins, he'd been in yellow by the third mountain stage five times and, in the other two, he took yellow that stage. In fact, in three of his wins, he took the jersey the first time he got to the mountains, and this year he lost time to Contador. So he's clearly not the same rider. But in the all-important third week, he will be.