Pete Sampras is playing too well to have to worry about the details of a tournament that could give him a place in tennis history.
After beating Carlos Moya, 6-3, 6-3, on Wednesday, Sampras said he was unaware that he had clinched a place in the semifinals of the ATP World Championship in Hanover, Germany.
"That's nice to hear," Sampras said after being told he had reached the final four. "It's certainly a good feeling to be here over the weekend."
Not feeling so good was Andre Agassi, who withdrew from the tournament because of a back injury.
Agassi quit in the third set of his match against Alex Corretja. He will be replaced in the round-robin draw by Britain's Greg Rusedski.
Sampras is seeking to become the first man to finish No. 1 in the world for six years in a row. He shares the record with Jimmy Connors.
Marcelo Rios, the only player who can threaten Sampras, trails by 33 points in the computer rankings and has to do better than Sampras in the season-ending championship.
But Rios, who was not scheduled to play Wednesday, lost his first match to Tim Henman and is battling a back injury. He now has to win his next two round-robin matches to reach the semifinals and stay in the chase.
The eight players are split into two groups and Sampras and Rios cannot meet until the semifinals.