The Spaniard is more likely to throw caution to the wind both because he is further back, and because he can act as a foil for Quintana.
Contador has no interest in finishing anywhere other than top of the pile as he bids to become the first rider since the late Marco Pantani in 1998 to achieve the Giro/Tour de France double in the same year.
"I'm very motivated for this last week. The Tour's not over," said the 32-year-old Spaniard, sitting fifth at 4min 23sec.
"My aim at this Tour is only the yellow jersey. I came here to win - I wouldn't be happy with a podium place."
Contador and reigning champion Vincenzo Nibali, a distant eighth after his Pyrenean disaster, tried to attack on the final climb in Monday's 16th stage. Nibali made his stick and then gained more ground on the descent to the finish in Gap, while Valverde also tried to distance the yellow jersey on the tricky downhill section off the Col du Manse.
Froome expects more of the same from his rivals.