Andy Murray has acknowledged that he will carry a degree of uncertainty over his fitness until he comes through a five-set match.
The three-time Major champion is currently preparing to play at the US Open, which will represent the 31-year-old's first Grand Slam in 14 months.
Murray says that he will look to "tough it out" if and when the time comes, but admits that it is an "important" step on his comeback trail after hip surgery.
The Scot told BBC Sport: "Having not played a five-set match for a long time, I won't know how my body will cope with that until I actually get there and do it.
"I'm sure I'll be able to tough it out if I need to - but it might not be particularly comfortable That's something I will find out if I'm in that situation.
"It is important for me to go through that and see exactly where I'm at, to see how I feel after playing an extremely long match. That will inform what I do over the next few months as well, maybe show I need to adjust things building up to Australia next year."
Murray faces Australia's James Duckworth in the opening round at Flushing Meadows.