PARIS (AP) — Stumbling on his way to the net, Roger Federer dropped his racket and fell to his knees on the red clay. Hardly the sort of grace and precision the world has come to expect from the 17-time Grand Slam champion. There were other unusual sights in Federer’s 6-4, 6-3, 7-6 (4) loss in the French Open quarterfinals Tuesday against his pal and Swiss Davis Cup teammate Stan Wawrinka. Rarely injured and appearing in a 62nd consecutive major, Federer received treatment on his right hand from a trainer during a second-set tiebreaker. For years and years, a dominant and confident force in tennis, Federer slumped in his changeover chair, head bowed, after falling behind two sets to none. So long superior to the younger Wawrinka, Federer was defeated for only the third time in their 19 head-to-head matches, and for the first time in five meetings at Grand Slam tournaments. During the eight French Opens from 2005 to 2012, Federer reached at least the semifinals seven times, including winning the 2009 championship to complete a career Grand Slam. But this is now the third year in a row that Federer has exited Roland Garros in the quarterfinals or…