Next week, for the first time in 40 years of ATP rankings, there will be no American men in the top 20. That’s because John Isner (pictured), who is 20th this week, is assured of dropping lower after losing Tuesday in the first round of the Rogers Cup to Vasek Pospisil of Canada 5-7, 7-6 (5), 7-6 (4). 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 U.S. men’s tennis. 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 no American men got that far there, way back in 1912, none entered.