Pete Sampras faces the tough task over the next three weeks of clinging to his world number one ranking, starting at the Eurocard Open in Stuttgart this week.

The 27-year-old is aiming to become the first player to head the rankings at the end of the year for six consecutive years.

He had breathing space yesterday, as each of the 16 seeds received first-round byes, and his first match is to be against Byron Black of Zimbabwe or German number one Nicolas Kiefer.

His search for ranking points has forced the American to play in Europe over the past few weeks. Usually in the autumn, Sampras picks his tournaments then flees home to Florida.

"It's a very important goal I'm trying to achieve," he said. "I'll do whatever I have to do to make it. If it means being away from home for five weeks, then so be it."

Also chasing top spot are Chile's Marcelo Rios and Australian Patrick Rafter. Like Sampras, both are struggling, Rios from a thigh injury, Rafter from a hip injury and general fatigue.

According to ATP Tour statistics, seven other players, led by Andre Agassi, are still in the fight to finish the year at number one. Agassi moved back into the top five for the first time in more than two years after defeating Slovak Jan Kroslak in the Czech Indoor final on Sunday.

Sampras has been allowed to start tomorrow in the hope that back problems that forced him out of last week's event in Lyon, France, might subside.

Yesterday, Michael Chang, the former world number two, was knocked out 7-6, (7/5), 6-3 by Frenchman Guillaume Raoux. Chang has been injured for much of the year and his ranking has slipped to 25th. He won the title at Shanghai this month then lost in the first round at Singapore.

Fellow American Jan-Michael Gambill beat Czech Daniel Vacek and another American, Todd Martin, knocked out Sebastien Lareau, who replaced Marat Safin of Russia, who was ill.