But a category 2 climb ensured a tough start, and then three more category 3 climbs, including one up to the finish, split the race to pieces, with Vincenzo Nibali (Bahrain-Merida) and BMC's Richie Porte finishing well off the pace, with their challenges for a good overall placing seemingly already over.
Porte's BMC teammate and overnight leader Rohan Dennis was similarly caught napping, and the race lead passed to Team Sky's Michal Kwiatkowski.
But that wasn't before the Polish road race champion and Valverde duked it out for the stage victory on the final climb, while a brave attack with just over a kilometre to go by Laurens De Plus saw the Quick-Step rider cling on for third place on the stage.
Kwiatkowski now leads the GC by 14 seconds from Valverde, while Sunweb's Wilco Kelderman is another 11 seconds back.
Watch Valverde and Kwiatkowski's ding-dong battle for the stage win in the video highlights above.
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