Nadal, right, congratulates Moya after his shock defeat in Miami

Moya took just one hour and 42 minutes to overcome his 19-year-old compatriot, who saved two match points before he lost his serve for the fifth time.

Moya, 29, now faces Agustin Calleri who beat France's Gael Monfils 7-5 6-4.

Nadal's exit came on the back of news that Andre Agassi had pulled out of the event with a chronic back problem.

Lucky loser Bjorn Phau replaced Agassi but went down 5-7 6-4 6-2 to Christphoe Rochus.

My physical condition is not my best now Rafael Nadal

Meanwhile, third seed David Nalbandian of Argentina beat American Paul Goldstein 3-6 7-5 7-6(2) in the second round.

Fifth seed Nikolay Davydenko saw off Mardy Fish 6-4 7-5, sixth seed Ivan Ljubicic beat Robin Vik 6-3 6-7 (2-7) 6-3, and 25th seed Marcos Baghdatis beat Alex Bogomolov Jr 6-2 6-4.

Nadal admitted he had been well below par against Moya, especially after picking up an ankle problem last week.

"My physical condition is not my best now, especially after I turned my ankle," said Nadal. "I have some problems when I play big points, when I go strong to one side.

"But that's not a special excuse. For sure I didn't play 100% but he played very good, too. He played with confidence.