NEW YORK (AP) — Only a few spots separate them in the seedings. Still, the considerable gulf between No. 1 Serena Williams and No. 4 Sara Errani was hard to ignore in their back-to-back matches Thursday at the U.S. Open. Williams, seeking her 17th Grand Slam title and second straight at Flushing Meadows, brushed off an ungainly slide onto her backside en route to a typically easy second-round victory, 6-3, 6-0 over Galina Voskoboeva in half-full Arthur Ashe Stadium.