New York, September 12

On high alert after a day of upsets during which Serena Williams was sent packing from the US Open, Novak Djokovic and Roger Federer made sure their names were not added to the list of shocks on Friday as they posted emphatic semi-final victories.

The tremors started early at Arthur Ashe Stadium with Flavia Pennetta crushing second seed Simona Halep 6-1 6-3, before Roberta Vinci rocked Flushing Meadows delivering one of the biggest upsets in tennis history with her semi-final win over Williams that punctured the American's calendar Grand Slam dream. Two wins from becoming the fourth woman to win all four majors in one year, a brittle-looking Williams crumbled as unseeded Vinci, playing in her first grand slam singles semi-final, battled to an improbable 2-6, 6-4, 6-4 win.

The results set the stage for an equally improbable all-Italian final on Saturday. "I don't want to talk about how disappointing it is for me," Williams told reporters. "I told you guys I don't feel pressure. I never felt pressure. I never felt that pressure to win here. I said that from the beginning." With the National Tennis Center buzzing over the exit of Williams, world No 1 Djokovic and second seed Federer restored order to the year's final grand slam.

Djokovic needed 85 minutes to secure passage to his fourth consecutive grand slam final, crushing defending US Open champion Marin Cilic 6-0, 6-1, 6-2. The demolition was the worst ever in a US Open semi-final, the three games lost one fewer than the four Yevgeny Kafelnikov managed against Lleyton Hewitt in 2001.

Federer, a five-time US Open winner, was equally efficient as he beat Swiss compatriot Stan Wawrinka 6-4, 6-3, 6-1. The all-time grand slam singles king with 17 titles, Federer heads into Sunday's final gunning to add to his record haul. He has not won a grand since 2012 Wimbledon. The final will mark the 42nd meeting between the two great rivals, with Federer holding a wafer 21-20 advantage. "Novak it's been more straightforward, my opinion," said Federer.

Vinci, a 300-1 shot to win the US Open when the tournament began, pulled off one of the most remarkable ever tennis upsets by ending Williams' streak of 33 consecutive match wins in the grand slams. A five-time doubles grand slam winner, 32, Vinci had never been beyond the quarter-finals in singles play at 43 majors.

In the other corner stood Williams, a 21-time grand slam champion who had lost only two matches all season and had not dropped a set against Vinci in their four previous meetings. Forced to wait a day after rain wiped out Thursday's semi-finals schedule, the weight of expectation appeared to take its toll on a 33-year-old who was chasing the first calendar Grand Slam since Steffi Graf in 1988.

Everything was going according to script as Williams easily took the opening set but things began to unravel after a composed Vinci registered a key break in the fifth game of the second that allowed her to even the match. With the contest slipping away, Williams tried to will herself back into the match, screaming and fist-pumping after each point and feeding off the support of the crowd. But with nothing lose, an undaunted Vinci continued to pressure Williams, who could not match previous great escapes.

While a stunned Vinci celebrated, a scowling Williams quickly departed a stunned stadium. "This is an incredible moment for me," Vinci said. "It's amazing. It's like a dream. I'm in the final. I beat Serena." Lost in the drama of the Williams match was a brilliant performance by Pennetta, who needed less than an hour to deal with Romanian Halep.

Pennetta, was a clear underdog but the 26th seed tapped into her vast experience and was not overwhelmed on the big stage. She had reached the quarter-finals at Flushing Meadows in six of the previous seven years, but the final will be uncharted territory.