Possible pitfalls in Serena's path to history

Top-ranked Serena Williams has some tricky challenges in her quarter of the US Open draw made Thursday, but the three-time defending champion remains a runaway favorite to make more tennis history. The 34-year-old American, who completed a "Serena Slam" of four major wins in a row by capturing Wimbledon last month, is trying to complete the first calendar-year Grand Slam since Steffi Graf in 1988 and match Graf's Open Era career record of 22 major titles. Russia's third-ranked Maria Sharapova, w