Second-seeded Mardy Fish of the United States advanced to the second round of the Delray Beach International Tennis Championships on Tuesday when German Bjorn Phau retired from their first-round match while trailing 0-5.
Fish, who won the Delray Beach title in 2009, took 20 of 26 points in the 20 minutes he spent on court. Fish was also a finalist at the tournament in 2003.
''I've been out here long enough to know not to take these kinds of matches for granted and move on,'' said Fish, who has been battling thyroid illness since November. ''Lord knows, I haven't been feeling the best the past couple of months.''
Kei Nishikori of Japan, who won his only career title here in 2008, beat Brian Dabul of Argentina 6-2, 7-6 (5). Nishikori, returning from elbow surgery in August 2009, will play James Blake in the second round.
Juan Martin del Potro of Argentina, working his way back onto the tour after right wrist surgery last year, had a 6-4, 6-1 first round win over Richard Berankis of Lithuania.
Once the 2009 U.S. Open champion secured the opening set, he took control of the match. He only allowed Berankis to hold serve once in the second set, in the fourth game.
''I think my first goal for this year is to play healthy,'' Del Potro said. ''After a year out it's very tough to come back. I'm improving day-by-day, match-by-match, and I'm improving week-by-week.''
Six players from the scheduled main draw have come down with flu-like symptoms.
Top seed Andy Roddick pulled out of the event on Monday. Radek Stepanek of the Czech Republic withdrew over the weekend. American Ryan Harrison was sick on court and lost his match on Monday.
On Tuesday, Phau and Jan Hajek of the Czech Republic abandoned matches feeling sick, and Michel Przysiezny of Poland never made it to the court.
Sixth-seeded Janko Tipsarevic of Serbia, making his first career appearance in Delray Beach, captured a tough 7-6 (14), 7-6 (1) first round victory over Ivo Karlovic of Croatia.
Karlovic, who lives in South Florida, lost in last year's Delray Beach final to Ernests Gulbis of Latvia. Gulbis is not attempting to defend his Delray Beach title.
