Chris Froome believes stage 16's individual time trial could be crucial in his bid to achieve a rare double at La Vuelta.
Team Sky's Froome is seeking to become only the third person to win the Tour de France and La Vuelta in the same year.
The 32-year-old Briton currently has a lead of one minute and one second over 2010 winner Vincenzo Nibali going into the final week of the race.
Froome will be expected to extend his advantage on Tuesday in a 40km time trial, a discipline which suits the four-time Tour de France winner.
But he is wary of the climbing that lies ahead in the final week, with summit finishes awaiting on stage 17 (Los Machucos) and 20 (Angliru).
On the final rest day, he said: "To be a minute ahead of my closest rival is a good position to be in after two weeks of racing and going into the final week.
"I've been looking forward to the TT. It's certainly going to be one of the more crucial stages that will decide this year's Vuelta GC.
"I'm not expecting to take huge amounts of time, but if I can extend my lead at all that would be fantastic.
"I take it one day at a time at the moment. Obviously Angliru is at the end of the week and that's looming in the back of my mind as well.
"The day after the TT we've got Los Machucos to think about which is tough as in a TT you can't really save much for the next day.
"Having said that, I'm certainly going to ride the TT with Machucos in mind and know that I'll need quite a lot to get up the steep summit finish."