Wout Poels has to prove form at Route de Sud if he wants to race Tour de France

Wout Poels, one of Chris Froome's key lieutenants, has been told that he must prove his form at next week's Route de Sud if he wants to race the Tour de France.

The Dutchman, in his third year at Team Sky, has endured a frustrating season having not raced because of a knee injury since finishing fourth at the Ruta del Sol in mid-February; he only has 10 race days to his name all season.

Poels has been training for the last month and is set to race the four-stage Route de Sud which begins on June 15.

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If he can show that he has recovered from his injuries, and also demonstrate his climbing powers, then he could be considered for a spot in Sky's Tour de France team.

Failure to alleviate concerns, however, will mean that Poels will not race July's Grand Tour and that would represent a blow to Froome.

"If Wout is on form, he's a pretty certain factor [he will race the Tour]," Sky's sport director Servais Knaven is quoted as saying in AD, a Dutch newspaper.

"But for us it is a wait and see. He has been out of racing for a long time and has only been training for a month.

"We want to see what his level is in a race and see how his knee holds up. In a training session you decide when you go hard and when you recover. It a race it can take up to five hours."