Rafal Nadal quits before Paris semifinals to rest

Paris • John Isner stayed on track for the last spot at the ATP Finals by beating Juan Martin del Potro 6-4, 6-7 (5), 6-4 in the Paris Masters quarterfinals on Friday.The American was the runner-up last year and needs to win the tournament to reach the finals in London this month."I've given myself a pretty good shot to qualify," Isner said. "But it's going to be very tough."Meanwhile, top-ranked Rafael Nadal pulled out with a right knee injury, and hopes to be fit to lead the London field.