Chris Froome's main goal in Thursday's 12th stage of the Tour de France will be to ensure that those rivals who have already slipped out of contention do not get back into the race.
The Briton leads Italian Fabio Aru by 18 seconds and France's Romain Bardet by 51 seconds and he will be watching them closely during a punishing 214.5 kilometre trek in the Pyrenees, ending with a short, brutal climb to Peyragudes.
Twice champion Alberto Contador and, to a lesser extent, Colombian Nairo Quintana, had bad days in the ninth stage in the Jura last Sunday, but Froome will not give them space.
"We don't want guys who have lost time to get back into the game," Froome said.
The last 50 kilometres of Thursday's stage are extremely brutal.
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The riders will tackle the climb up to the Port de Bales (11.7km at an average gradient of 7.7 per cent), a descent to the foot of the Col de Peyresourde (9.7km at 7.8 per cent), a very short downhill and the final ascent to Peyragudes (2.4km at 8.4 per cent) with gradients sometimes reaching 20 per cent.
"It's quite savage. I think if someone blows in those few hundreds of metres (at 20 per cent), there could be some really significant time gaps," said Froome.
"It's one of the key stages of this year's race."
Froome is likely to race conservatively.
"The number one priority is not to allow some guys to come back into the GC game and of course for me personally to keep a close eye on Aru.
"I will stick to him like glue."
Thursday's stage is made even trickier by the fact that the following one is a punchy 101km trek in the Pyrenees - the kind of short stage that is hard to control.
"It's hard to hold anything back on a stage like tomorrow but the following day will be in the back of our minds," he said.
In 2013, in a similar stage, Team Sky were blown apart after repeated attacks early on and Froome was quickly isolated by his rivals.
