Andy Murray has admitted that his energy-zapping first two US Open matches could take their toll on his body as the competition progresses.
"In these conditions, obviously it can take its toll later on in the tournament," he told Sky Sports News.
"But unfortunately you don't always have the luxury of winning matches in straight sets. Sometimes you have to fight through if you're not playing your best.
"Thankfully the last three sets were fairly comfortable in terms of the scoreline, otherwise I could have been out there much longer and it would have been very tough to recover from."
Murray faces Brazil's Thomaz Bellucci in the third round later today.