Jack Draper was dumped out of the Miami Open in the second round after Reilly Opelka took their two sets into tie-breaks and won both.
The mammoth American, 6ft 11in tall, was landing serves that looked almost unreturnable.
Draper had come to Florida buoyed by a run to the quarter-finals in Indian Wells in only his second ATP Tour event following almost eight months out with an arm injury.
But his hopes of a repeat were dashed as Opelka came through the two tie-breaks to win 7-6 (7-3) 7-6 (7-0).
Opelka set the tone with four successive aces in the opening game and he did not let up, finishing with 25 aces and 47 winners.
Draper, who has never made it beyond the second round in Miami, made just six unforced errors but could not find a chink in his opponent's armour.
Defeat leaves Draper at risk of slipping further down the rankings going into the clay-court swing after losing the British No 1 spot to Cameron Norrie this week.
Katie Boulter is through to the third round, though, after opponent Clara Tauson retired early in the deciding set of their rain-hit clash.
The early stages were stop-start because of showers and, when the match did finally get going properly, Boulter was unable to close out a 5-3 lead in the opening set, shouting in frustration after losing in a tie-break.
The British No 3 then trailed 2-0 in the second set but fought back to take it and had won the first game of the third when Dane Tauson, the 17th seed, decided she could not continue because of injury and called it a day with Boulter leading 6-7 (4-7) 6-4 1-0.
Watch the ATP and WTA Tours, live on Your Site or and the , giving Your Site customers access to over 50 per cent more live sport this year at no extra cost.
