Mardy Fish sent defending champion Andy Murray crashing out of the Sony Ericsson Open with a straight-set win in the second round in Miami on Saturday.
The third-ranked Briton, who had a first-round bye as the third seed, led 3-1 and 40-0 in the first set; but was caught up by the 101st-ranked American Fish at 3-3.
The 28-year-old American went on to play more confidently than the 22-year-old Briton and took the set 6-4.
Murray served the first game of the second set but Fish broke it and was always in the lead with big serves and good returns before taking the set 6-4 again and winning the match after an hour and 33 minutes.
Murray was the second big name to bow out of the tournament after the world number two Novak DJokovic, who Murray defeated in last year's final, suffered a shock defeat to Belgian Olivier Rochus on Friday, also in the second round.
And the defeat by Fish means Murray will lose his number three ranking to Rafael Nadal who saw off big-serving American Taylor Dent 6-3 6-3 in only 70 minutes.
Top seed Roger Federer won his opening match 6-3 6-3 against lucky loser Nicolas Lapentti.
Seventh seed Croatian Marin Cilic cruised into the third round with a 6-1 6-3 victory over Frenchman Stephane Robert, while ninth seed Chilean Fernando Gonzalez beat Lu Yen-Hsun of Taiwan 6-4 6-4.
Fifth seed Swede Soderling defeated Australian Peter Luczak 7-6 (7-5) 6-0 and 10th seed Spaniard Fernando Verdasco crushed Israeli Dudi Sela 6-1 6-2.
In the women's event, top seed Svetlana Kuznetsova, Venus Williams and Agnieszka Radwanksa have booked their fourth-round berths.
Kuznetsova took an effortless 6-2, 6-3 win over Hungary's Agnes Szavay while Venus beat Italian Roberta Vinci 6-1, 6-4 and sixth-seeded Pole Radwanksa beat former World No. 1 Serb Ana Ivanovic 7-5, 7-5.