Hewitt wins as cramps stop Kokkinakis

Veteran Lleyton Hewitt has overcome the brutal heat to safely advance to the second round of the US Open, but Australian young gun Thanasi Kokkinakis is out after succumbing to severe cramping in New York.

Hewitt progressed to a potential second-round showdown with Bernard Tomic when Kazakh Aleksandr Nedovyesov quit with a right shoulder injury while trailing Australia's former world No.1 and 2001 Open champion 6-0 7-6 (7-2) 1-0.

Kokkinakis was on track to pull off a major upset until beginning to cramp after he took a two-sets-to-one lead over Wimbledon semi-finalist Richard Gasquet.

The score was locked at two sets apiece - 4-6 6-1 4-6 6-3 - when the 19-year-old was forced to call it a day after dropping serve to trail 2-0 in the deciding set.

As Kokkinakis winced in pain while being treated courtside and even resorted to serving under-arm, 34-year-old Hewitt showed signature grit to squeeze out the vital second-set tiebreaker in his Open opener.

"Yeah, it was hot and humid out there. Obviously sweating a lot, which was just hard. But it's hard for everyone out there as well," Hewitt said.

"I felt like I got off to a great start. Came out and executed my game plan perfectly.

"He's an awkward opponent because I wanted to be aggressive and play on my terms, but it's a bit hit-and-miss out there so you're trying to make him play that extra shot as well.

"If you don't get enough on it, he's capable of hitting winners. I was happy to play a really good tiebreak."

Ajla Tomljanovic, James Duckworth and qualifier John-Patrick Smith also joined Kokkinakis as first-round losers on Tuesday.

Tomljanovic was unable to convert after taking the opening set in a 6-7 (1-7) 6-2 6-4 first-round loss to Italian Karin Knapp, while Smith also had opportunities in a 6-1 3-6 7-5 7-6 (7-4) defeat at the hands of experienced Russian Mikhail Youzhny.

Korean teenage sensation Hyeon Chung routed Duckworth 6-3 6-1 6-2 in just one hour and 36 minutes.