Andy Murray's plans for next week's Australian Open suffered a blow when he lost his opening round-robin match at the Kooyong Classic in Melbourne.
Murray is back in the world's top 10 after his Qatar Open success
The British number one, who began the season by winning the Qatar Open, lost 6-1 6-4 to Marat Safin and admitted he was feeling the effects of jet lag.
"I guess it takes a few days once you get here after the long trip to feel 100% again," Murray told his website.
"I didn't get off to the best start but I feel all right, just a bit tired."
Murray also claimed he had been surprised by the timing of his match, saying: "We obviously got bumped by the match in front.
"I was doing some running on the track this morning and I hadn't had my lunch too long before the match.
"So in some of those long rallies I felt like it was just about to all come up."
The Kooyong Classic is an eight-man exhibition tournament and Murray is confident he will improve in his second match against Ivan Ljubicic on Thursday.
"It's all preparation for the Australian Open," Murray, 20, said. "Obviously you want to play well, but the most important thing is to get in 100% shape for Monday.
"To get the chance to play in front of a crowd with umpires and line judges is much more realistic than just playing practice."
Former world number one Safin will play Andy Roddick for a place in the final of the eight-man exhibition event.
"It is such a long time since I played such good tennis," said Safin. "I was pretty surprised how well I played."
Roddick, who has won the title at Kooyong in each of the past two years, was totally dominant as he raced to a 6-3 6-0 victory over Croatia's Ljubicic.
The tournament also features Nikolay Davydenko and Marcos Baghdatis, while Roger Federer could make a late appearance if he has fully recovered from a virus.
The Swiss world number one had pulled out but was back in practice and organisers said he might play a match later this week.
For sure I can't play, I can't even hit slowly
David Nalbandian was also forced to withdraw after suffering back spasms and is now a doubt for the first Grand Slam of the season.
The Argentine, who finished 2007 in great form, winning back-to-back Masters titles in Madrid and Paris, was training with Safin when the injury happened.
"I need to rest, take treatment and we'll see how it goes," said Nalbandian, the world number 10.
"It came up after about 30 minutes of training. I tried to finish, Marat and I were playing points. But I had to stop.
"For sure I can't play, I can't even hit slowly. It's better to rest and recover the muscle. We have to wait and see."
Nalbandian was due to face Fernando Gonzalez in the first round of matches, but the Chilean was handed a walkover and will meet Baghdatis for a place in the final.
Baghdatis, runner-up to Federer in the 2006 Australian Open, beat Davydenko 6-4 4-6 6-1.
Gonzalez did get a workout at least, beating stand-in Brydan Klein, the 2007 Australian Open junior champion, 7-6 6-4.