The British No 1 lost 3-6, 6-3, 6-4, to the world No 71, Jan Kroslak, in the third round of the Legg Mason Classic. The Slovak has now beaten Henman in all of their three meetings.
Henman got off to a good start, taking the opening set and getting an early break in the second set. He then lost his way, whether through failing concentration or because of bad light, it was hard to tell. Henman was frustrated at his change of fortunes and his first serve, the thermometer of his game, started to disappear.
"I didn't play with the same authority in the second set, and once he got back into it he grew in confidence," Henman said. "I know I have to keep working on my consistency and will be preparing hard for the US Open."
Henman now hopes that six matches in the past two weeks will be an adequate preparation for the Open.
Pat Rafter, was forced to withdraw from the RCA Championships after a third-round victory over Daniel Nestor of Canada 7-6, 6-2, in Indianapolis. Lingering tendinitis in his right shoulder has plagued the world No 4 for the past three months.
The Australian is still hoping to be fit for the defence of his US Open crown. The final Grand Slam of the year starts a week on Monday and Rafter is bidding for a third consecutive title.
"I'm pulling out to give myself a little more time for the US Open," Rafter said. "I knew there was a bit of a problem here. I didn't think it would progressively get worse and worse."
Monica Seles, who like Rafter, is also struggling to be fit for the US Open. She has had a chronic shoulder problem during the last couple of years, but a stress fracture to her right foot is causing her concern at the moment.
The American put her injuries aside by defeating Elena Likhovtseva of Russia 7-6, 6-3, in the du Maurier Open, in Toronto on Thursday and stays on course for a fifth consecutive title in the event.
Martina Hingis, of Switzerland, recovered from a 3-0 first-set deficit to win 10 games in a row en route to beating Chanda Rubin, of the United States, 6-3, 6-1. The world No 1 now plays Spain's Arantxa Sanchez-Vicario, who beat her compatriot Conchita Martinez 7-6, 6-1, in the quarter-finals.Reuse content