NEW YORK — Rafael Nadal made his earliest US Open exit in a decade Friday, suffering his first Grand Slam defeat after leading by two sets, while Serena Williams rallied to keep her calendar Slam dream alive. Spanish eighth seed Nadal, whose 14 Slam titles include the 2010 and 2013 US Open crowns, fell victim to 32nd-seeded Italian Fabio Fognini 3-6, 4-6, 6-4, 6-3, 6-4 at Arthur Ashe Stadium. Nadal had not lost so early on the New York hardcourts since a third-round ouster in 2005 by American James Blake. The 29-year-old left-hander had been 151-0 in Slam matches when leading by two sets. “He played great,” Nadal said. “It's not that I lost. He wins. I'm not happy but I accept he was better. I didn't play bad. I fight until the last point. It was not enough.” Fognini imposed seven consecutive service breaks upon Nadal in the fourth and fifth sets, smacking 70 winners past the iconic star in a fantastic effort. “I can't describe how happy I am,” Fognini said. “It was very tough. To do it against Rafa, two sets down. It was an incredible match.” Fognini, 32, booked a last-16 date with 18th-seeded Spaniard Feliciano Lopez, who eliminated Canadian 10th seed Milos Raonic 6-2, 7-6 (7/4), 6-3. Nadal lost to Fognini on clay at Rio de Janeiro and Barcelona earlier this year, but had bounced back with a triumph in July's Hamburg final. It was Fognini's first win in 18 tries on hardcourt against a top-10 rival and made him the first Italian in the US Open last 16 since Davide Sanguinetti in 2005. Women's world No. 1 Serena, meanwhile, battled through mistakes and the tension of her quest for tennis history. Serena fought back to defeat 101st-ranked US compatriot Bethanie Mattek-Sands 3-6, 7-5, 6-0 at Arthur Ashe Stadium and needs only four more triumphs to complete the first calendar Slam since Steffi Graf in 1988. Serena, holder of all four major titles, also seeks her 22nd career Slam singles crown to match Graf's Open Era record. The 33-year-old American went to three sets for the 10th time in 24 Grand Slam matches this year and stayed perfect, eight of those fightbacks after first-set defeats. “I'm not trying to live on the edge,” Serena said. “I don't think I came out too slow. I think Bethanie came out really well. I had to adapt to her game and I finally got some rhythm going toward the end of the second set.” Serena struggled early, hitting only 52 percent of first serves in the first set, when she also made half her 28 unforced errors. But Williams found her form late in the second set and dominated thereafter. Three-time defending champion Serena, who could reach her first Grand Slam final without facing a top-10 foe, next plays US 19th seed Madison Keys. Top-ranked Novak Djokovic moved a step closer to his 10th career Slam crown and third of the year by defeating Italy's Andreas Seppi 6-3, 7-5, 7-5. Djokovic took his 31st win in a row over Italian foes, his 11th from Seppi, since losing to Filippo Volandri in his ATP debut at Umag in 2004. Next up is Spanish 23rd seed Roberto Bautista Agut, who advanced when 14th-seeded Belgian David Goffin retired while leading 6-2, 7-5, 3-6, 1-3. A Grand Slam record 13 men have retired from matches at this tournament. Croatian ninth seed Marin Cilic barely escaped making the earliest exit of any defending champion since Andre Agassi in 1999 before outlasting 56th-ranked Kazak Mikhail Kukushkin 6-7 (5/7), 7-6 (7/1), 6-3, 6-7 (3/7), 6-1. Cilic next meets French 27th seed Jeremy Chardy, who ousted Spanish seventh seed David Ferrer 7-6 (8/6) 4-6, 6-3, 6-1. Venus Williams, 35, eased sister Serena's path to the final by ousting the top-rated rival on their side of the draw, defeating 12th-seeded Swiss teen Belinda Bencic 6-3, 6-4. Bencic, 18, inflicted the most recent defeat upon Serena last month in a Toronto semi-final, but fell to 0-4 against Venus, who fired 31 winners against 15 unforced errors. — Agencies