U.S. Open 2015: Rain delays Serena's grand slam quest

How is that possible?

Rain postponed action at the year's final major, meaning Williams will now play Roberta Vinci in the last four as part of a packed Friday in New York.

Besides the women's semifinals, the men's semifinals will also be contested.

We should have known rain would play havoc with the schedule late in the second week at the U.S. Open -- it has routinely happened in recent years, affecting the men's final.

Weather issues won't be a problem starting next year, since a retractable roof will be in place over Arthur Ashe stadium.

Williams, if she progresses Friday, would face either world No. 2 Simona Halep or Vinci's fellow Italian, Flavia Pennetta, in Saturday's final. The American is bidding to become the first player since Steffi Graf in 1988 to win all four grand slams in the same season.

Halep and Pennetta begin play Friday, followed by Williams and Vinci.

World No. 1 Novak Djokovic meets defending champion Marin Cilic before an all-Swiss battle between Roger Federer and Stan Wawrinka concludes play.

(CNN)