MONTREAL -- Next week, for the first time in 40 years of ATP rankings, there will be no American men in the top 20.
Isner was a semifinalist at the hard-court tournament last year and failed to defend those points.
It's the latest indication of the recent decline of men's tennis in the United States, which produced Grand Slam champions such as Bill Tilden and Don Budge, John McEnroe and Jimmy Connors, Pete Sampras and Andre Agassi.
At Wimbledon in June, for the first time in 101 years, no men from the country reached the third round at the All England Club. The last time that happened there, way back in 1912, none entered.
The U.S. Open, which starts Aug. 26, will mark 10 years since the last time an American man won a Grand Slam tournament -- Andy Roddick at the 2003 U.S. Open.
Roddick was a fixture in the top 10 until a series of injuries hampered him shortly before he retired during last year's U.S. Open.
According to the ATP, at least one American man has appeared in the top 20 every week since the first computer rankings came out on Aug. 23, 1973. The new rankings will come out Monday.
Raonic said he felt no added pressure to keep the Canadian winning streak going.
"I'm very proud and happy for the guys that have been winning," he said. "But it doesn't affect myself personally.
"It's great to have this kind of good results, but I've got to take care of my business for myself."
Peliwo, who is 19 and won the boys' title at Wimbledon last year, staved off a match point in the second set with what he called a "lucky" shot, and then moved on when Jarkko Nieminen stopped playing in the third set because of a hamstring injury.
Peliwo will face 66th-ranked Denis Istomin of Uzbekistan in the second round on Wednesday.
Rafael Nadal, an 11-time Grand Slam champion who hasn't played since a first-round loss at Wimbledon, teamed with Pablo Andujar to fight off two match points and beat David Ferrer and Feliciano Lopez 6-7 (2), 6-4, 12-10 in doubles.
In other singles matches, 13th-seeded Fabio Fognini beat Marcos Baghdatis 1-6, 6-1, 6-1, Alex Bogolomov got past Michael Llodra 6-2, 4-6, 6-3, and Youzhny defeated Jurgen Melzer 6-4, 7-6 (3). No. 9 seed Kei Nishikori of Japan defeated Italian Andreas Seppi 4-6, 7-5, 6-1 in the second round.