A leg-weary Andy Murray succumbed 6-3 6-4 to Andy Roddick in the Cincinnati Masters quarter-finals on Friday.
Murray will head to Nick Bollettieri's academy ahead of the US Open
Murray had three break points early in the match but could not convert and Roddick took control, breaking in game eight and then twice in the second set.
"I wasn't going into the match expecting to win," said Murray, who was playing his 14th match in 17 days.
"I considered pulling out when I woke up in the morning and about a half an hour before I went on."
Roddick had already lost twice this year to the 19-year-old Scot, with Murray beating him en route to his first ATP title in February and, most recently, at Wimbledon.
The victory sets up a meeting with Fernando Gonzalez, who beat David Ferrer 6-2 6-4.
I think I've shown I can consistently play well in back-to-back weeks
"I wanted to win, of course," said Roddick. "I really put a lot of stock into this match and I knew I'd have to play well and be intense if I wanted to win."
Murray looked drained on court in Cincinnati and after failing to convert his early chances, Roddick made the breakthrough to go 5-3 up.
The American then raced into a 5-2 lead in the second set and, although Murray got a break back, Roddick wrapped up the win on his fourth match point.
Murray reached the final in Washington and the semis in Toronto in the weeks before Cincinnati, and he is looking forward to a short break.
He will then turn his attention to the US Open, which begins on 28 August, and will spend next week preparing at Nick Bollettieri's academy.
"I think mentally it's been a big battle, and physically as well, I think," said Murray.
"I've played 14 matches in 17 days. I think I've shown I can consistently play well in back-to-back weeks."
He added: "I'm going to relax for a couple of days. There's no need to do anything. I think I've done enough the last few weeks to earn a few days' rest.
"I've got a fitness trainer coming to work with me in Bollettieri's for three, four days. Then I'm probably going to go to the US Open Thursday."