Rainer Schuettler's troubled season continued as the German went out of the Pacific Life Open to Wayne Arthurs. The sixth seed went down 6-1 7-6 (7-3) in the Masters Series event, and has now lost his opening match in five of his six events so far this season.
There was no such trouble for defending champion Lleyton Hewitt, Andre Agassi or Tim Henman, who all won easily.
But Gustavo Kuerten, last year's beaten finalist, and 10th seed Paradorn Srichaphan also crashed out.
Kuerten, seeded 15th, was beaten 6-4 7-5 by young American Taylor Dent.
Dent broke to love in the 12th game to take the opening set and, after four consecutive breaks at the start of the second, he booked his place in the third round with a drop volley on his third match point.
Srichaphan fell victim to Tommy Haas whose first-round win was his first victory in 16 months.
Haas took just 68 minutes to beat Srichaphan 6-1 6-2 and now faces Albert Costa.
Mark Philippoussis, the 12th seed, was another loser, going down to Mikhail Youzhny, while Tommy Robredo, Martin Verkerk, Feliciano Lopez and Robby Ginepri were the other seeds to fall.
But Hewitt had no trouble against Thomas Johansson, cruising to a 6-2 6-3 victory in his opening match.
While Agassi had things easy against Spain's David Sanchez, winning 6-2 6-2.
Henman took 62 minutes to beat Canadian qualifier Simon Larose 6-3 6-2 to set up a third-round meeting with Alex Corretja, who beat Robredo.
Already in an easy-looking section of the draw, Henman's draw now looks even better after the defeats of fellow seeds Robredo and Schuettler.