The pair cited fatigue as explanation for their sluggish performances on Monday night, the Fed Cup team-mates losing tough first-set tie-breaks with nothing left to give in the second set.
Martinez, who fell 7-6, 6-2 to Belgium's Dominique Van Roost, said it was just too late in the year to hold such an important tournament.
"It's very hard to keep the year going so long," said the seventh seed, who reached the Australian Open final way back in January. "We end the year on 22 November and then we have to start in January. It's like go, go, go."
The usually fleet-footed Sanchez Vicario is known as the game's most tenacious battler. But after the first set, there was no evidence of the trademark intensity in her eyes.
"Everybody is coming to this tournament really tired and my body just feels it," said the fourth-seeded Sanchez Vicario, a 7-6, 6-1 loser to the Romanian Irina Spirlea.
"I still tried my best but the second set I didn't have much energy left," she said. "We play because we like it, because it is our profession, but we are human beings."Reuse content