Cruelly, the Irishman was edged out of second by his Etixx-QuickStep teammate Julian Alaphilippe but hung on for third after a typically gutsy display.
Martin came into the race as one of the favourites having been second, fourth, and sixth in the past. All looked to be going to plan when he approached the final climb towards the front of the peloton.
Such was his team’s desire to set him or Alaphilippe up for glory, they even reeled in teammate Bob Jungels who had wriggled clear of the bunch a few kilometres earlier.
Martin kept his powder dry all day but when the final ramp up the Muur de Huy climb loomed, he made his way to the sharp end of things where all the big names waited to pull the trigger.
In previous years, the 29-year-old has left his attack late and just ran out of road but he was determined to take up the pace-setting this time. He pressed for home with 300m to go — but locked onto his wheel was the irrepressible Valverde ready to pounce.
The Movistar man jumped clear for his fourth win in the race, with Alaphilippe hanging on for second.
Meanwhile, Team Sky rider Sergio Henao is set for a period of inactivity after queries were raised about his blood values for the second time in his career.
The Colombian has, of his own volition, withdrawn from racing of until the matter is cleared up.
A statement from the team said he had not failed a drugs test and will work for him in addressing the questions that have emerged.
Elsewhere, Ireland’s Philip Deignan is up to 13th overall at the Giro del Trentino after finishing 18th on yesterday’s mountain stage.
He’s 38 seconds down on teammate Mikel Landa going into today’s penultimate day.