Sastre had a quiet, understated opening to the tour. After a lacklustre opening time-trial, he remained relatively restrained in the opening mountain stages in the Pyrenees and opted to stay defensive and follow the wheel of his main rivals. This allowed his CSC teammate Fränk Schleck to claim the yellow jersey at the finish to stage 15 at Prato Nevoso. However, on the crucial 17th stage, Sastre showed his class and mountain climbing prowess, attacking at the bottom of the final climb of the day, Alpe d'Huez, finishing 2 minutes and 15 seconds ahead of Evans, claiming both the stage win and the yellow jersey. Sastre, knowing that a slender lead over a strong time-trialist like Evans may not have been enough to secure overall victory going into the penultimate stage, sought to gain an advantage of at least a couple of minutes over his closest rivals.