Yoshihito Nishioka crashed out in the first round of the Brisbane International on Tuesday, falling to world No. 29 Victor Troicki.
Nishioka eventually fell 6-4, 7-5 in a match that was suspended due to rain after Troicki won the first set on Monday.
"I wanted to win," said Nishioka, who felt rib pain during the second set. "I didn't play terribly. I came up short in some small areas."
Nishioka, who reached the main draw through qualifying, is lacking match fitness after devoting his offseason to rehabbing his elbow.
"Given I wasn't well prepared, I did pretty well," he said.
Earlier, Kei Nishikori advanced to the quarterfinals in men's doubles as he and partner Dominic Thiem of Austria knocked off the second seeds, Finland's Henri Kontinen and Australia's John Peers, 1-6, 6-3, 12-10.
Nishikori rarely plays doubles except at this tournament as part of his buildup to the Australian Open. Last year, he reached the semifinals here.
On Wednesday, world No. 5 Nishikori, the third seed in the men's singles draw, will face American qualifier Jared Donaldson before his doubles quarterfinals later in the day.