Valkenburg, Netherlands ? The already depleted Tour de France lost another top rider Tuesday when Alejandro Valverde of Spain crashed during the third stage in which world champion Tom Boonen of Belgium took the overall lead.

On a day when cycling’s showcase race crossed into three countries, Germany’s Matthias Kessler won the hilly stage under a blazing sun, surging ahead on the last climb.

Valverde crashed in the middle of the main pack, causing a small pileup. The Tour Web site said he fractured his right collarbone. Grimacing in pain, he received medical treatment before being placed on a gurney. He most likely will return to Spain for surgery.

Also knocked out of the race because of crashes were Fred Rodriguez of the United States and Erik Dekker of the Netherlands, reducing the field to 172 riders.

Norway’s Thor Hushovd, who held the lead entering the day, slipped to fourth overall after struggling on the final climb and finishing 63rd. Rogers, the time-trial world champion, is second, one second behind Boonen. George Hincapie of the United States is third.

Boonen will wear the leader’s yellow jersey in his home country Wednesday for the fourth stage.

Alejandro valverde of spain, foreground, is being helped by Tour de France chief doctor Gerard Porte after crashing. Valverde suffered a race-ending collarbone injury during Tuesday's third stage.

“It’s something that happens maybe only once every 10 years, so I think it will be special,” he said.

The world champion’s jersey “is the most beautiful of all and now I’m wearing the second most beautiful jersey of all,” Boonen said. “I’m on a good schedule for the future.”

He also holds the green jersey awarded to the best sprinter, and is aiming for that honor again at the finish in Paris on July 23.

Kessler is part of the T-Mobile squad that lost its leader, Jan Ullrich, to doping accusations before the race began Saturday. Ullrich, the 1997 Tour winner, was forced out of the race along with Giro d’Italia champion Ivan Basso and others because of alleged links to a doping ring in Spain.

“But we are professional cyclists,” Kessler said. “For us, it is important to hold our heads high and look forward.” He said he has been in contact with Ullrich but did not elaborate.

Kessler held off sprinters who had been favored to win this leg of the three-week race in which the riders touched into Luxembourg, Belgium and the Netherlands.

He was followed over the line by Australian teammate Michael Rogers, who was five seconds back. Lampre rider Daniele Bennati was third, with Boonen fourth. It was the first stage win for 27-year-old Kessler in four Tours.

Boonen said he was slowed by a tire problem in the final stretch and “couldn’t stand up or sprint” because he feared the tire would fail completely.

He also complained about the large crowds lining the route as riders buzz by at 40 mph. There have been several accidents involving spectators this year. Hushovd was struck Sunday by a large cardboard hand held by a fan, cutting his arm. French rider Sandy Casar said he was struck by a spectator Tuesday.

“There were some very, very dangerous moments in the final and I wasn’t too happy about it,” Boonen said. “It was crazy.”

Dekker, who rides for Rabobank, cut his face and was to take precuationary brain scan, the Tour doctor said. Rodriguez, of the Davitamon-Lotto team, injured his shoulder and wrist, the doctor said. His team said he sustained a concussion but broke no bones.

Rodriguez rode into a big hole in the road, teammate Robbie McEwen said.

“I heard a huge crunch,” McEwen said. “It was just such a horrible crash because he just went straight down.”

A total of six riders were hurt in three crashes.

Christopher Horner, another American on McEwen’s team, also was injured in a crash. He finished the stage but it was unclear if he would ride Wednesday.

Also injured were Casar and another Frenchman, Sebastien Joly.