Slovakian Peter Sagan raises his arms in triumph at the end of stage five on the Tour de FranceSlovakian Peter Sagan raises his arms in triumph at the end of stage five on the Tour de France. (AFP Photo/Jeff PACHOUD)
Defending champion Chris Froome (Team Sky) and the other overall contenders finished in or close to the main group as overnight leader and Olympic road race champion Greg Van Avermaet (BMC) retained the yellow jersey.
Belgian Philippe Gilbert sparked the hostilities early on the uphill finish of the 204.5km ride from Lorient, but the Quick-Step rider failed to open up a significant gap on the chasing bunch.
Van Avermaet, wearing the yellow jersey, then pulled to the front in a bid for the stage win as the finish line approached but peaked too early.
The race leader was left powerless when Sagan sped past on his left. Colbrelli pushed the Slovakian all the way but, as he did on stage two, finished second best.
Sagan said following the yellow jersey had helped land him the stage.
"I'd like to thank Greg (Van Avermaet) because he did me a favour when he went for it, I don't know if he did it on purpose but he dropped a lot of people," said Sagan, who has tightened his grip on the points classification's green jersey.
Asked if it would be a battle all the way to Paris with Fernando Gaviria for the green jersey prize, Sagan said: "I hope not!"
The pair have two stage wins each from the first five and Sagan had predicted Tuesday the Colombian might struggle with the climbs.
"The fact he wasn't in the sprint was good for me," Sagan, who now leads Gaviria by 33 points, said.
Despite a spectator-friendly slug up the final hill, race designer Thierry Gouvenou told AFP he had expected more fireworks.
"I'm not sure the riders knew how to take advantage of it, the stage really could have been much more interesting," he said of the course some were describing as riddled with traps.
- 'Mur' thrills expected on stage six -
With five categorised climbs to be negotiated over the narrow, tree-lined Brittany roads a breakaway was to be expected.
An escape group featuring Sylvain Chavanel embarked on a long-range bid with Van Avermaet's BMC doing most of the work at the head of the chasing peloton, and Bora joining the chase late.
Thursday's sixth stage is expected to shake up the peloton as it culminates in the double ascension of the feared Mur de Bretagne climb, a 2km long and 6.9 percent gradient affair.
On paper, it looks a step too far for Sagan. Lighter, more agile riders like Van Avermaet, Alejandro Valverde, Julian Alaphilippe and Gilbert are expected to shine.
"Tomorrow's finish will be very difficult to control over the final 2km," Sagan said. "I'll try my best to win but you saw all that today."
"The Mur de Bretagne is much harder than this," said Van Avermaet, who would not rule Sagan out of contention for the sixth stage.
"Valverde or Alaphilippe will be there, it's their kind of race," he added.
"But Gilbert and Sagan will be there until the end."
The double ascent of the Mur may tempt a yellow jersey contender to steal a march on his many GC rivals, and is keenly awaited as a key stage on the Tour.
-- Blue Sky --
Sky were omnipresent over the final kilometres of racing and Luke Rowe said he felt they had been getting a more positive reaction from the crowds after being booed at the presentation.
"We have actually been getting quite a complimentary reception, of course for every thousand cheers you might get one negative person but you take that in your stride, I've got broad shoulders, it's in one ear and out the other for those who don't appreciate what we're doing."