British number two Jack Draper was knocked out of the Miami Open in the second round with a 7-6 (7-3) 7-6 (7-0) defeat by Reilly Opelka.
The 24-year-old lost two tie-breaks to the big-serving American, who wrapped up the win inside 93 minutes.
Draper had headed into the tournament after an impressive run to the quarter-finals at Indian Wells - featuring a win over Novak Djokovic - following nearly eight months out with an arm injury.
However, he struggled against the powerful 6ft 11in Opelka, ranked 67th in the world, who fired down 25 aces and 47 winners.