Today's time trial marks the start of the real race

VITRE, France -- Tour de France favorites, it's time to step up.

The race begins in earnest Saturday with the first long time trial on a Tour marked by crashes and a doping investigation that has stripped the event of elite riders.

After an opening week when top riders took few risks and the glory belonged to sprinters Robbie McEwen and Tom Boonen, the time trial should help reveal the true contenders in a depleted field.

McEwen's win in Friday's sixth stage was his third this year and 11th in nine Tours.

The Australian won in characteristic fashion, muscling past other sprinters. Among them was Boonen, the overall race leader who clung to the prized yellow jersey but is frustrated not to have another stage victory to go with the four he has from previous Tours.

Stars of the fast and relatively flat first week -- McEwen, Boonen and other sprinters -- will cede the limelight next week. And Boonen will almost certainly cede the yellow jersey as well. That will now belong to all-arounders and mountain-climbing specialists once the Tour heads south into the Pyrenees.

In fact, Boonen's fourth consecutive day in the race leader's yellow shirt today could be his last. The Belgian is not among those expected to shine in the time trial, which favors racers able to ride quickly and steadily over long distances.

Perhaps not since 1999, when Lance Armstrong first took control of the Tour, has the outcome of a time trial seemed so uncertain. The seven-time Tour champion excelled in the discipline, winning nine of the 14 time trials of 10 miles or longer.

Of the four people who beat Armstrong in long time trials, only two are racing: American David Zabriskie of Team CSC and Saunier Duval's David Millar, a Briton back from a two-year doping ban.