Serena Williams’ pursuit of the calendar-year Grand Slam is over, as the 21-time major champion was defeated by unseeded Italian Roberta Vinci 2-6, 6-4, 6-4 in the US Open semifinals Friday.

Williams was attempting to become the first woman to win all four majors in a season since Steffi Graf in 1988. Williams also could have tied Graf for the second-most Grand Slam singles titles behind Margaret Court’s 24.

Vinci will face countrywoman Flavia Pennetta, who defeated No. 2 seed Simona Halep ea

Serena Williams won her match against her sister Venus Williams in three sets Tuesday at the U.S. Open to advance to the semifinals. (Al Bello/Getty Images)

With a powerful ace, Serena Williams capped her biggest win of the tournament.

She’ll have to win two more matches in order to complete the calendar Grand Slam and tie Steffi Graf with 22 Grand Slam titles, but the atmosphere inside Arthur Ashe Stadium Tuesday night felt like a U.S. Open final.

Playing in front of a sell-out crowd, Sere