American Bobby Reynolds defeated the big serving 8th seed Ivo Karlovic of Croatia 7-6 (5) 2-6 6-3 in the first round of the Houston tennis event and set up a match against fellow Ryan Sweeting in round two.
Despite Karlovic hitting 19 aces, his ground strokes let him down and the world no.116 Reynolds used his chances to claim a surprise win.
Wild card holder Kevin Aderson of South Africa booked his place in the second round by beating the Brazilian Joao Souza 6-3 6-4.
Anderson will face American Sam Querrey next.
Also through is Tatsumo Ito of Japan, who dismissed his fellow countryman Go Soeda 6-4 7-5.