Andy Murray feels he is "playing with the house's money" after his narrow escape against Robin Haase at the US Open.
The Scot was hit by cramp throughout his body after winning the first two sets of his opening-round match on Monday and admitted he was very close to defeat.
Haase served for the fourth set but could not take advantage of his opponent's troubles.
Murray told the BBC: " I was lucky to come through yesterday, I could easily be on the plane home today. So I'm playing with the house's money and I'll just try and go out there and do the best I can."
The eighth seed practised in the heat of the day on Tuesday with British number two James Ward, who is still hoping to get into the main draw as a lucky loser.
Murray reported no ill-effects from his ordeal but will no doubt welcome the fact his second-round match against German Matthias Bachinger will not be played until Thursday, giving him two days to fully recover.
He still does not know exactly why the cramp came on but suspects he got his eating and drinking wrong.
Murray said: "I felt physically ready, it was just a strange situation yesterday. Hopefully I'll pull up fine over the next couple of days.
"Before I went to bed yesterday I felt fine, I woke up this morning with no aches or pains or stiffness. That suggests it was more down to something I hadn't eaten or drunk or I was lacking in something before I went out there, rather than me physically not being in good condition.
"I just need to do all the right things. I don't play my next match until Thursday so I'll have time to hydrate and get enough fluid in the body, and eat as best I can."
Qualifier Bachinger beat Radek Stepanek on Monday for his first grand slam victory - some result considering the German was not even supposed to be in New York.
His ranking, now 235, was too low to make the cut for qualifying, and he was so far adrift that he did not even travel to the States in the hope that people would pull out.
"I didn't think I would get in," said the 27-year-old. "They called me last Monday. I flew here from Europe on Tuesday, I arrived in the afternoon and I played on the Wednesday.
"So my preparation was not very good, but from the beginning I had a very good feeling. Sometimes life is crazy."
Bachinger had been playing on clay back home in Munich but somehow the unusual preparation worked as he breezed through qualifying.
More surprisingly still, he then eased past Stepanek, one of the trickiest customers on tour, and has not lost more than three games in any set.
He said of the Stepanek win: "I played unbelievable. I think it was my best match ever.
"Stepanek is not a bad guy. He has much experience. But everything went for me and I played really well. It was the best tennis day of my life maybe ."
Bachinger and Murray have never played each other in a professional match but they were briefly junior rivals - the German is a month older.
"I'm really looking forward to playing him," said Bachinger. "When we were 14 we played each other a few times. Now it's a different match, for sure, but I'm really looking forward to it. We'll be on a big court.
"I won one time, 7-6 in the third. It was in Italy. I've never forgotten that because in juniors he was really, really good. Then I think I lost to him three times.
"He was fighting for every ball, just like he does now. You could already see that he would be a top star."
The German will go into the clash as a big underdog but will no doubt take encouragement from Murray's struggles on Monday and his up and down form this season.
Bachinger said: "I saw the end of the match. I saw that he was cramping a little bit. He had some problems, but at the end he won, like he usually does.
"I was very surprised because he is normally really fit. I've never seen him cramping before - but he's human, not a machine.
"The good thing for me is that I'm in good form. In tennis you always have chances. Of course I know it will be really tough, but I just want to go out there and enjoy every minute, every ball. That's my goal for this match."