Defending champion Alberto Contador knows he must make his move in the Alps if he is to win a fourth Tour de France.
Contador is a superior rider against the clock to the Schleck brothers, but insists he cannot wait until Saturday's 42.5-kilometre penultimate day's time-trial, with Cadel Evans also in contention.
With six days of racing and the Alps to come, the Spanish Saxo Bank-SunGard team leader lies four minutes behind yellow jersey incumbent Thomas Voeckler (Europcar), but crucially 1min 45secs behind Andy Schleck (Leopard Trek), 1:54 adrift of Evans and 2:11 behind Frank Schleck (Leopard Trek).
Speaking on the Tour's second rest day, Contador said: "With my current position overall, I can't win the Tour on the time-trial in Grenoble.
"There are three very important days in the Alps.
"Right now the differences are very big and the Galibier (on Thursday) is probably where the most time differences will be because it is the hardest stage.
"If I want the victory I will have to attack and have a good rhythm from the start.
"Alpe-d'Huez (on Friday) is very short, so not so good, but Pinerolo (on Wednesday) could be dangerous if the weather is bad."