He believed that Primoz Roglic, who has won the last two years, would be more active.
But the Slovenian only took in 20 seconds on the Norwegian and has 1.36 up to the lead from his third place.
- The slopes were not so steep and there was a headwind so I sought as much protection as possible.
(Guillaume) Martin went on the attack but I knew he would have to fight the headwind.
The last three kilometers I knew I would have to keep the leader jersey, says Eiking to his own stable Intermarche-Wanty.
New tough mountain stage today
Martin, second in the summary 54 seconds behind, was finally only four seconds ahead of Eiking at the finish line in Picu Villuercas after 166 km.
Today, another tough mountain stage awaits over 197 km between Navalmoral del Mata and El Barraco.
- My legs feel pretty good, says Eiking and hopes to keep the shirt over Monday's rest day.
The crowd with the top riders in the summary was just over ten minutes behind the stage winner Romain Bardet who won his first Grand Tour stage in four years.
- I have waited a long time, says Bardet after his solo victory.
The three-week classic will finish in Santiago de Compostela on Sunday the fifth of September with a 34 km long flat individual pace stage.