US Open 2015: Rain could make final splash before roof is ready

New York: With a historic calendar Grand Slam attempt shattered before the weekend, a US Open women's final missing much of its anticipated marquee magic now faces the threat of thunderstorms.

Italy's Roberta Vinci and Flavia Pennetta are set for a Saturday afternoon trophy showdown at Arthur Ashe Stadium in its final weekend of matches before a retractable roof is ready for the 2016 tournament. "One Italian will win for sure. It's an incredible moment," Vinci said.

Arthur Ashe Stadium's not-yet-completed roof and a video screen test pattern are reflected in a puddle on the stadium's tarp-covered court.

Vinci defeated top-ranked defending champion Serena Williams 2-6, 6-4, 6-4 while Pennetta ousted Romanian world number two Simona Halep 6-1, 6-3. Williams, who holds all four major titles until the women's final is played, was bidding for the first calendar Grand Slam since Steffi Graf in 1988 and a 22nd Slam singles crown to match Graf's Open Era record.

But all that vanished when Vinci pulled one of the great stunners in tennis history. "I don't want to talk about how disappointing it is for me," Williams said.

And now a dreary weekend forecast calls for a 65 per cent chance of thundershowers on Saturday and a 75 per cent chance for the same on Sunday for the men's final between top-ranked Novak Djokovic and second-ranked Roger Federer.

Rain had forced the men's final to be delayed until Monday from 2008 through 2012, pushing the US Open to construct the new roof, the superstructure framework for which stands around Ashe this year.

In addition to the first all-Italian women's Grand Slam singles final, the men's doubles final is also on Saturday's jeopardized schedule. That features Britain's Jamie Murray and Australian John Peers against the French duo of Nicolas Mahut and Pierre-Hugues Herbert.

Pennetta, 33, and Vinci, 32, are each in their first Grand Slam final seeking the top prize of $3.3 million (2.9 million euros), with the runner-up taking home $1.6 million.

Pennetta leads the career rivalry 5-4 and won their most recent meeting in the 2013 US Open quarterfinals. If she hoists the trophy in her 49th Slam appearance, Pennetta would have the most tries of any Grand Slam women's champion, two more than France's Marion Bartoli when she won at Wimbledon in 2013.

"It's going to be amazing for me to win this tournament. This is going to be a chance to do something amazing," she said.

The only Italian woman to win a Grand Slam singles title was Francesca Schiavone at the 2010 French Open. The only other woman to reach a Slam final was Sara Errani, who lost the 2012 Roland Garros final.