Australia's Chris Guccione has made a first-round exit in the ATP's Pilot Pen tournament, losing 7-5 6-3 to Spain's Guillermo Garcia-Lopez.
The Victorian left-hander and world No.88 last week reached the doubles quarter-finals with Lleyton Hewitt at the Beijing Olympics.
Meanwhile Argentine teenager Juan Martin del Potro, who has won four straight titles on the ATP tour, cited exhaustion for his withdrawal from this week's event in Connecticut.
"It is difficult to still play a lot of matches," del Potro said.
"I want to recover for the US Open (starting next week). Unfortunately I have to pull out of this tournament."
Del Potro, ranked a career-best 17th in the world and seeded third, was coming off tournament victories in Stuttgart, Kitzbuhel, Los Angeles and Washington, where he won on Sunday.
The winner of 19 successive matches had been scheduled to play on Tuesday.
Lucky loser Jesse Levine of the United States will take his place in the main draw.
Promising young American player John Isner defeated Russian Igor Kunitsyn 6-4 6-4 in the first round.
The hard-serving Isner closed out the match with a 217 km/h against Kunitsyn, who reached the Washington semifinals last week.
Isner next faces second-seeded Ivo Karlovic.
Also, fellow American Wayne Odesnik beat France's Sebastien Grosjean 7-5 6-4.
A pair of Belgians advanced; Steve Darcis and Olivier Rochus, who will meet fourth-seeded Igor Andreev after beating another Russian, Evgeny Korolev 6-4 6-4.
Darcis progressed when Vince Spadea of the United States retired with a lower back injury while trailing 7-5 5-0. Nicolas Lapentti of Ecuador also had to quit with a left knee injury while Fabio Fognini was ahead 6-4 4-4.
In women's play, No.5 Patty Schnyder of Switzerland defeated Jill Craybas 6-4 7-6 (7-2), repeating her win over the American at the Beijing Olympics last week.
Schnyder was knocked out of the Olympics by Austria's Sybille Bammer in the second round and said she still felt the effects of the 18-hour flight from China to Connecticut during Monday's match.
"Generally it is tough to come from Beijing," Schnyder said.
"It is tough on your legs. It is just your body needs more time."
The (30-degree) temperature didn't help either.
"I felt really weak in the second set," Schnyder said.
"Luckily there was a little breeze that cooled me down. It was tough conditions."
Eighth-seeded Dominika Cibulkova of Slovakia, the runner-up at Montreal this month, retired because of heat illness after losing the first-set tiebreaker 9-7 to Stockholm winner Caroline Wozniacki of Denmark.
