The Spaniard was attacking over the top of the final climb when he fell in a turn on the descent, sustaining an injury to his hand that required surgery.
“Samuel Sánchez sustained multiple superficial injuries in a crash in the final kilometer of today’s stage at Pais Vasco. He has extensive abrasions all over the body including his hands. He has a contusion on one of his knees but luckily he didn’t sustain a head concussion in the fall," his team doctor Max Testa said.
"The X-rays at this point are all negative so we don’t think there are any broken bones. But, Samuel had a laceration of one of the extensor tendons of his fourth digit on the left hand. They are currently treating that surgically to re-attach the tendon and luckily it was a partial lesion.
"The plan is to take Samuel back to the hotel tonight and re-evaluate his condition on Saturday morning before the final stage. Given the degree of his injuries it is very unlikely that he will start but we will make that call then.”
Sanchez remounted after his fall and finished the stage. He is 12th overall, 34 seconds behind race leader Alejandro Valverde (Movistar) with the 27.7km time trial the only stage remaining.