Fifth-seeded French Open champion Mirra Andreeva of Russia showed a hook off a slow start to beat Anastasia Potapova 5-7, 6-4 6-3 on Monday and punch her ticket to the US Open quarterfinals.
In a dramatic final game, Potapova lost her footing leaning for a shot, falling to the ground and writhing in pain.
Andreeva, who later called Potapova "a pretty good friend," rushed over and helped assist Potapova to the side of the court where she received treatment on her left knee during a medical timeout.
She returned to the court to finish the game, the two women embracing after Andreeva floated a backhand winner down the line to close the match.