|US Open, Flushing Meadows, New York|
|Dates: 25 August-8 September Coverage: Live radio and text commentary on Andy Murray's matches, plus commentary every day from 18:00 or 18:30 BST on BBC Radio 5 live sports extra|
Andy Murray said his body let him down as he suffered with cramp in his opening match against Robin Haase at the US Open.
The Briton won 6-3 7-6 (8-6) 1-6 7-5 after three hours and eight minutes on a hot afternoon in New York.
However, he struggled physically from the start of the third set and was in danger of a shock first-round exit inside Louis Armstrong Stadium.
"I was in a good position, and then my body failed me," Murray told BBC Sport.
"I panicked, because you don't know what to do. I got broken at the beginning of that third set, and you think: 'What do I do? Do I try to conserve energy or do I try to finish it in three sets?'
"I don't really know how I managed to get through."
Murray, 27, said he felt cramping in several parts of his body and he was unable to serve at much over a tame 100mph in the third and fourth sets.
"It's not the worst I have ever felt necessarily, but it's the worst I have ever felt after an hour and a half of a tennis match," he added.
"That's what was worrying about it, is it came after such a short time.
"I've played four-and-a-half, five-hour matches and felt pretty awful afterwards, but not after an hour and a half."
With nerves and physical conditioning apparently not behind the issue, Murray plans to look for other explanations ahead of his next match.
"Maybe I'll speak to a nutritionist and look at what I had eaten the last three, four days," he said.
"I don't think I was that dehydrated, because I needed to go to the toilet when I got off the court.
"I don't know exactly what happened, but I will try to get to the bottom of it before I play again."
|Robin Haase||Andy Murray|
|60||1st serve %||61|
|69||1st serve win %||60|
|42||2nd serve win %||51|
|7/19||Break points won||6/13|
|Match time: 3hr 8 min|
Haase, the world number 70, had his own physical issues to deal with and was unhappy that he was not allowed treatment for a foot problem.
"I wanted to get treatment and I didn't get it," said the Dutchman.
"I've never heard before that the physio can deny treatment, or just say 'I will get the doctor and at the next changeover you will get a pill'.
"The trainer saw me and he tells me that a pill is enough. If I ask for treatment, I should get treatment."
Murray will play German qualifier Matthias Bachinger in the second round on Wednesday or Thursday.