2015 US Open women's semifinals

Serena Williams is just two wins from completing the most difficult feat in sports: The Calendar Grand Slam. Can she get past Italy's Roberta Vinci to make her fourth consecutive US Open final? And who will face her on Saturday? No. 2 Simona Halep or Flavia Pennetta? Join WTA Insider at 11am ET for the US Open semifinals, starting with Halep vs. Pennetta, followed by Serena vs. Vinci.