By Julien Pretot

CHERBOURG, France (Reuters) - Chris Froome's rivals need to be more aggressive if they are to prevent the Briton from winning a third Tour de France title and reap the benefits of offensive tactics, Alberto Contador's sports director said on Sunday.

Speaking to Reuters before the start of the second stage from Saint Lo to Cherbourg a day after the Tinkoff team leader suffered heavy bruises in a crash, Sean Yates said Contador could not be the only rider to attack.

"The general consensus, which is logical, is that you can't sit back and let Sky dictate things. They have the defending champion, the guys have shown great form this year," said the Briton, who led Bradley Wiggins to his Tour title in 2012 with Team Sky.

"It's not only us who have to take the race on, it's obviously the likes of (Australian Richie Porte's) BMC and (Nairo Quintana's) Movistar. That might profit us and maybe profit Movistar more," he added.

"Everyone is kind of scared sometimes of losing what they've got but nothing ventured nothing gained. The ultimate price is first place."

Last year, Froome smashed his rivals in the first mountain stage with brutal acceleration in the climb up to La Pierre St Martin and they never recovered.

"It's on Sky to control the race a lot and we'll take our chances. There are some crucial stages and the most important is that we don't concede too much time on the first mountain stage as it happened in previous years," Yates said.

"That's what (Miguel) Indurain would do back in the day: take a chunk of time in the first time trial or the first mountain stage and it's important to recoup that, to minimize the losses and take our chance to take time."

Contador, as well as Frenchman Romain Bardet (AG2r-La Mondiale), usually have an all-in approach to races, while Quintana, runner-up to Froome in 2013 and 2015, has a more conservative attitude, last year waiting for the last climb of the three-week race to launch a big attack.

"In my opinion it's better to throw caution to the wind like Alberto has done on multiple occasions and reap the possible benefits," said Yates.

Contador had tried his luck in 2015, too, but he was too weak after winning the Giro d'Italia.

"Last year he did the Giro and that took a lot out of him - he found out pretty quickly that the Giro had taken a lot out of him while this year his season was based around the Tour so I think he feels a lot fresher," Yates said.

Contador, however, had a bad night on Saturday after his crash, and he was still suffering on Sunday morning.

"He wants to take it as easy as possible until the crucial part of the race," said Yates.

(Editing by Ed Osmond)