FOR Australian Mark Renshaw, this year's Tour de France is the highlight to a new and challenging chapter in his career after spending three years at the service of British world champion Mark Cavendish.

When the pair went separate ways with the disbandment of HTC-Highroad last year, Cavendish took his talents to the British Sky line-up.

Renshaw, meanwhile, joined the Dutch Rabobank team and became lead sprinter instead of lead-out rider for Cavendish.

Considering their success as a duo, it was not surprising that Renshaw's switch from friend to foe in competition would attract plenty of attention.

Renshaw's new role meant he no longer had to focus on giving his all in a 65km/h bunch sprint from 500 metres out to help someone else, such as Cavendish, jump out from behind his rear wheel and sprint clear to another win.

Instead, Renshaw - as Rabobank's principal sprinter - now has to play the patience game and wait until the 200-metre mark before sprinting to the line.

Renshaw has already raced in his new position many times this season. So far he has one stage win in the Tour of Turkey and several top-five placings.

But he knows racing as a lead sprinter in the world's biggest event is totally different altogether. Adding to the challenge is that at this year's Tour, he does not have a lead-out train like the one he was a part of at HTC-Highroad to support him.

He is not the only sprinter in that department. Australian Matt Goss, and Germans Andre Greipel and Marcel Kittel have strong trains, and Argentinian Juan Jose Haedo has a secondary strength line-up. But without the trains to help them this year are Cavendish, American Tyler Farrar, Slovakian Peter Sagan and Italian Alessandro Petacchi.

That is because their teams have riders vying for a top place in the overall classification, requiring all but one or two teammates to ride at their service.

Making life harder for Renshaw is that the one Rabobank rider who had been assigned to work for him in the Tour, Dutchman Maarten Tjallingii, withdrew from the Tour on Tuesday night after the third stage, which he finished with a fractured hip sustained in one of the many crashes.

''My role has changed. I pretty much don't have a team around me to help me in the finish … it's freestyling to the maximum,'' Renshaw said before Wednesday's 214.5-kilometre fourth stage from Abbeville to Rouen in which he and Cavendish crashed heavily inside the last three kilometres.

To make up for a lack of manpower, Renshaw knows he will have to race smart and feed off the work of the big trains like bottom feeders to a shark.

On his side is that he is regarded as one of the smartest riders in the bunch. ''I am really going to have to rely on that,'' he said.

''I am going to have to pick the right wheels and pick the right moment. And I'll need a bit of luck. Without that, I don't think I will be able to succeed.''

It is not lost on either that many of those who will be in his way are his former HTC-Highroad teammates who share of tactical and personal knowledge of each other. ''I have been teammates with Goss, Cavendish, Greipel, Greg Henderson [now Lotto-Belisol),'' Renshaw said. ''Two-thirds of the front of the bunch in the sprints I have been teammates with. I know them all really well. It's just whether or not I can succeed in upsetting the apple cart a bit.''