Tim Henman’s career hit rock bottom last night as he suffered the ignominy of being beaten by a player ranked at 416 in the world. John Isner, a former collegiate player at the University of Georgia, who was granted a wild card into the Legg Mason Tennis Classic in Washington, came from behind to secure a 4-6, 6-4, 7-6 victory over the British No 2.

Henman, the world No 73, saved two match points in the tenth game of the final set but found himself 6-3 down in the deciding tie-break. He clawed another point back but then double faulted to seal his fate in a tournament that he won in 2003.

It was Henman’s worst defeat — in world ranking terms at least — since he lost to Dimitry Tursunov, who was then ranked 152, in the second round of Wimbledon in 2005 and meant that his US hard-court campaign got off to a calamitous start.

In the face of mounting pressure to retire, Henman has insisted that he is not yet ready to walk away from the game, but surely it is only a matter of time before defeats of this manner begin to take their toll on the former world No 4.

Isner, at 6ft 9in, is the second-tallest man on the ATP Tour, and it comes as no surprise that his serve is his key weapon. The 22-year-old from North Carolina hit 18 aces last night as he advanced to the second round of an ATP Tour event for the first time.

Henman, 32, had headed to the United States in the hope of getting some match practice in before the US Open, which begins later this month, after a disappointing Wimbledon in which he lost in the second round for the third successive year.

He will now head to Montreal for the ATP Masters Series event with his confidence in tatters and his doubles victory on Monday, when he teamed up with Mahesh Bhupathi to beat Lee Hyung Taik and Michael Russell 6-2, 7-5, offers little compensation.

Jamie Murray, the Wimbledon mixed doubles champion, and Eric Butorac, of the United States, lost 7-6, 2-6, 10-6, against Wesley Moody and Todd Perry while Alex Bogdanovic, the British No 3, was also a first-round loser, offering little resistance in a straight-sets defeat by Robin Haase, of the Netherlands.

Lindsay Davenport will return to the WTA Tour next month after the birth of her first child.