Serena Williams Ousts No. 1 Simona Halep at Australian Open

United States' Serena Williams celebrates after defeating Romania's Simona Halep in their fourth round match at the Australian Open tennis championships in Melbourne, Australia, on Jan. 21, 2019. Kin Cheung/AP Photo

MELBOURNE, Australia—As Serena Williams made her way out to the Australian Open’s main court during pre-match introductions, the voice booming over the stadium’s speakers implored spectators to welcome “the world’s No. 1 player—from Romania, Simona Halep.”

Oops.