Nick Kyrgios has pulled out of the ATP Tour's Delray Beach Open just hours before his first round match against Tommy Paul.

The top-seeded Australian has withdrawn from the singles tournament, but will still take part in the doubles draw.

Kyrgios' withdrawal means that all four Australians have failed to progress beyond the first round of the ATP 250 tournament in America.

"I'm dealing with a little bit of a left wrist injury; been dealing with it for the last week or so," Kyrgios said.

"Some sort of tendon thing. Apart from that feeling pretty good."

Lucky loser Daniel Elahi Galan Riveros will take the 24-year-old's place in the draw.

Kyrgios will still partner countryman Jordan Thompson, who retired in his singles defeat to Serbia's Miomir Kecmanovic, in the doubles.

Queenslander Bernard Tomic, who entered the main draw as a lucky loser, lost his opening round match 6-2 3-6 6-2 to Germany's Cedrik-Marcel Stebe.

Fifth-seeded Aussie John Millman suffered a 3-6 6-4 6-2 defeat to Japan's Yoshihito Nishioka in the first round of the 

tournament.

In his first match since his epic five-set defeat to Roger Federer at the Australian Open last month, Brisbane native Millman started well and broke Nishioka in the second game before going on to claim the opening set.

Three breaks of serve, two to Nishioka, in the final three games of the second set gave him the momentum as he levelled the match at a set apiece.

Millman dropped his serve in the fourth and final games of the third set as his challenge faded in an encounter which ended just shy of the two-hour mark.