The most demanding, exhausting one-day race of the professional road-racing calendar starts at 11 a.m. Sunday in Compiegne, France, just north of Paris.

Indeed, more than 20 percent of the course used for the 103rd Paris-Roubaix hardly qualifies as a “road” at all, in modern terms. Nearly 55km of the 259km route consists of 26 sections of bone-rattling, sometimes dangerously slick cobblestones.

Known variously as the “Hell of the North” and the “Queen of the Classics,” Paris-Roubaix is one of the most dramatic events in professional cycling. Partly cloudy skies are forecast for race day, but rain fell over northern France off and on Friday, and for many of the cobbled sections, the damage is done; the pave is already muddy and slick. And strong crosswinds, which often deny weary riders any respite on the paved sections between cobbled bits, are expected.

The Queen’s champions have included Tour de France greats Eddy Merckx and Bernard Hinault (who won thrice and once, respectively), but today, the race is the province of one-day classics specialists, such as Belgian Peter Van Petegem (Davitamon-Lotto), who won in 2003, and the big Swede Magnus Bäckstedt (Liquigas-Bianchi), who won the 2004 edition in six hours, 40 minutes. Both Van Petegem and Bäckstedt will line up for the race this year, along with a half-dozen other riders dubbed as favorites in a race that is as wide open as it has been in years.

Leading that short list is 24-year-old Belgian Tom Boonen (Quick Step), who took last Sunday’s cobblestone classic Tour of Flanders in grand style, leaping away in the final 10km from a lead group of five – a group that included Van Petegem - to win by half a minute. Boonen also had a strong showing at Wednesday’s Ghent-Wevelgem, a race he won last year, though he did not make this year’s final selection, finishing 26th, 31 seconds off the winning time.

Boonen has complained of a sore wrist dating to a crash at the Three Days of De Panne, and following the finish in Wevelgem even questioned whether he would race Paris-Roubaix. He later recanted his statement, saying all systems are go. Boonen will be flanked this year by 2001 Roubaix winner Servais Knaven.

Boonen shocked the cycling world when he finished third in his Paris-Roubaix debut in 2002 at just 21 years of age, while riding for U.S. Postal Service; he took ninth last year. Asked if his win at Flanders changed the dynamic for Roubaix, Boonen told VeloNews: “I think I’m in the same position I was in before the Tour of Flanders. I think I was the favorite anyway. It doesn’t change a lot. At Roubaix there will be the same riders as Flanders, and they will all do the same as they tried to do there – they will try to beat me.”

Added Boonen’s Quick Step team director Patrick Lefevre: “The only advantage for Roubaix is that we don’t have to be nervous anymore. The other teams are sitting nervous, and I hope they panic. If the other teams go and panic, it’s good for us.”

Only eight riders have ever accomplished the Flanders-Roubaix double in the same year, and one is Davitamon-Lotto’s Van Petegem, in 2003. Last year, Van Petegem had a badly timed puncture and had to settle for sixth, 17 seconds behind Bäckstedt.

After finishing third at last week’s Tour of Flanders, unable to match Boonen’s race-winning attack, Van Petegem sat out Ghent-Wevelgem in favor of a long training ride Wednesday. He was seen scouting the course’s new cobbled sections Friday alongside teammates Nico Mattan, winner at Ghent-Wevelgem Wednesday; Belgian national champion Tom Steels; Leon Von Bon; and two-time Roubaix top-10 finisher Henk Vogels. With rested legs, a strong team and one Roubaix victory under his belt, a Van Petegem victory would surprise few.

Also a podium candidate is Bäckstedt, whose victory last year confirmed him as a classics rider of the modern era. He held off Tristan Hoffman and Roger Hammond to take the biggest win of his career.

At Flanders, Bäckstedt was part of an early break, setting the pace on the flats but dropping off on the course’s hilly climbs.

“All in all, it was good training for Paris-Roubaix,” said Bäckstedt. “The condition is good, so I am optimistic.”

But after making the final selection at Ghent-Wevelgem on Wednesday, Bäckstedt crashed, and like Boonen he has complained of wrist pain, a serious concern over the jarring cobbles of Paris-Roubaix. An X-ray failed to find a fracture, but the wrist remains sore “and will be even more painful on the cobble sections,” the big Swede said. “I will try not to think about the pain and not to focus on it."

Asked to name his top rivals, Bäckstedt ticked off Boonen and Van Petegem, as well as three of his breakaway mates from Wednesday: Fassa Bortolo’s Fabian Cancellara and Juan Antonio Flecha, and Norwegian Thor Hushovd (Crédit Agricole).

Not on Backstedt’s list, surprisingly, is American George Hincapie (Discovery Channel), who has finished within the Roubaix top 10 five times, although he has never reached the podium. In 1999 and 2001 Hincapie matched his best placing in Roubaix, crossing fourth. Hincapie has also taken sixth place twice, in 2000 and 2002, and finished eighth last year.

An illness forced Hincapie to miss Milan-San Remo in March, but he says he’s been riding himself back into form every day since. At the start of Ghent-Wevelgem, VeloNews asked Hincapie if he’d be saving anything in his legs for Roubaix.

“I had a break since San Remo, so I wasn’t able to race for nine days, so I think I can race as hard as I can here and it would probably be good for me for Sunday,” Hincapie said. “Normally I come here and I’ve been at a good level for a while, but hopefully I’m just coming back up to my level.”

Joining Hincapie at Discovery are Russian workhorse Viatcheslav Ekimov; Tony Cruz, 16th at Ghent-Wevelgem; former cross-country star Ryder Hesjedal; Canadian Michael Barry; and Belgians Stijn Devolver and Leif Hoste.

Last year’s third-place finisher, Roger Hammond, is still uncertain going into Sunday's race. Hammond crashed hard in Wednesday's Gent-Wevelgem, and Discovery director Dirk Demol said the team is awaiting the doctor’s approval.

“We just want to make sure he won't do any more damage to the thumb by racing on Sunday,” Demol said on the team’s website.

On Thursday, Hincapie, Hoste, Devolder, Cruz and Hesjedal rode the first nine cobbled sections of the Paris-Roubaix course, which skips the Arenberg forest but includes new pavé. Ekimov and Barry were scheduled to arrive Friday from the Circuit de la Sarthe, leaving the final spot for either Hammond or Volodymyr Bileka.

Fassa Bortolo brings a pair of hopefuls to Roubaix: Fabian Cancellara, fourth last year, and Juan Antonio Flecha, who hopes to be the first Spaniard to win in Roubaix. Flecha rode strongly at Flanders, finishing 12th, and both riders made the lead group at Ghent-Wevelgem, where Flecha was overtaken in the final 100 meters by Mattan in a finale that some said had more to do with press motorcycles and luck than with strength, stamina and will.

Perhaps. Others say that’s bicycle racing. But come Sunday, one thing is certain: Whoever crosses the finish line first at the historic Parc Municipal de Sports velodrome in Roubaix will need the right combination of strength, stamina, will - and yes - luck.