The battle for the 2011 Vuelta a Espana's overall starts with a vengeance on stage four of the race on Tuesday, with no less than 50 kilometres of classified climbs and a summit finish at more than 2,000 metres above sea level.
"It's not going to be absolutely decisive but it will be a big day for the favourites," race director Javier Guillen told Cycling Weekly.
"Climbs like the Angliru later in the race will have a much more serious effect on the overall."
"But at Sierra Nevada we'll start seeing who is really going to be in the frame, and in that sense it'll be very important."
Although breakaways are very likely given there is a first category climb, the Alto de Filabres, almost as soon as the 170 kilometre stage starts, the consensus of opinion is that the favourites will not be on an all-out attack.
Mountain specialists like David Moncoutie (Coifidis) are likely to try and get away for a repeat win on the same climb where the 2010 King of the Mountains took a solo victory in 2009, the last time the race went up there.
Instead, Sierra Nevada, the summit finish, is likely to produce a war of attrition among the overall contenders. And the climb will be an excellent test of riders' overall condition. Although the 2011 Vuelta goes up the 'easy way' to Europe's most southerly ski station - on the main, well-surfaced approach road rather than up the far steeper and narrower Alto de Monachil climb, which sometimes forms part of the ascent - its relentless 23 kilometres of climbing have only a couple of false flats midway through for riders to recover.
The steepest sections, too, are at the bottom of the ascent, which usually encourages a large chunk of non-climbers to sheer off almost immediately and leave the peloton down to around 60 or 70 within a couple of kilometres. Then it's a long, near slow-motiion grind with riders slowly getting spat out of the back. Under normal circumstances, we could expect around 15 or 20 to be in the front group by the finish.
There are other factors that may affect the day's racing other the climb itself. First the heat, which is forecast to be around a sizzling 35 degrees minimum throughout the entire stage, held mostly on on narrow, constantly undulating roads across the Sierra de Filabres and Sierra Nevada mountain ranges.
The organisers have also laid on some 'ambushes', like the third category climb to Blancares that immediately precedes Sierra Nevada. The climb itself is not too tricky, but the descent off Blancares on little-used, treelined roads is treacherously narrow, and twisting - and goes on for nearly 20 kilometres.
Temperatures at the summit of Sierra Nevada are forecast to be a balmy 23 degrees, but the real joker in the pack could be the wind. As the road approaches the ski station itself it is on increasingly exposed roads, and if a half-gale gets up - as it often does on Sierra Nevada - initally small gaps between riders who are dropped can increase very fast.
For the main contenders, Sierra Nevada is not a climb, this year, where the Vuelta will be won. But coming so early in the race, it will be an excellent test of who is in good form and who will be taking an early flight home.
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