Sampras showed lack of match sharpness after playing virtually no tennis in last three months. This was only his third match after hip and back injuries. He had 29 unforced errors, while Agassi had only six in the one-hour match.

Agassi, who replaced Sampras as top-ranked player this year, had to save break points in his first two service games.

Sampras covered the net well at the start of the match and hit several spectacular volley winners. But Agassi weathered the storm and went a key break up in the fifth game. Sampras was undone by two double-faults as he dropped his serve.

Agassi is assured of finishing the year as No 1, a distinction Sampras held the last six years running. Sampras has dropped to No 5. Agassi, who had lost his three previous matches to Sampras and trails 11-16 in careermeetings, is now 2-0 in the round-robin tournament. Sampras is 1-1, still with a chance of advancing to the semifinals.

Fourth-ranked Thomas Enqvist, riding a hot streak in the indoor season, beat No 6 Nicolas Kiefer 6-4, 7-5.