Roger Federer’s hopes of claiming a record-extending 20th Grand Slam title ended on Wednesday when he was beaten 5-7 6-3 6(8)-7 4-6 by Juan Martin del Potro at the U.S. Open. Del Potro, who swept aside Federer in the 2009 final at this same Flushing Meadows, now faces world number one Rafael Nadal of Spain […]