Serena Williams is reminding the world why she just may be the greatest women's tennis player of all time.

The 40-year-old legend upset No. 2 seed Anett Kontaveit in the second round of the US Open on Wednesday, winning 7-6 (4), 2-6, 6-2.

Williams, who has said she will "evolve away" from the sport after the tournament, turned in a vintage performance two days after she defeated Danka Kovinic 6-3, 6-3 in her opening match.

Over her career, Williams has won 23 grand slam singles titles, which is the most in the Open era and one behind the all-time record held by Margaret Court. She has also won four Olympic gold medals and over $94.5 million in prize money.

She and her older sister, Venus, transformed the sport when they became professionals as teenage phenoms. They've teamed up for many grand slam doubles titles and will play together at this year's Open. Their first match is on Thursday.

Williams takes pictures with fans at Arthur Ashe Stadium after her win on Wednesday

Williams returns a shot during Wednesday's match

Fans cheer on Williams on Wednesday

Williams reaches for a shot

Williams reacts after winning the first set tiebreaker

Source; CNN sports