Williams took a dramatic first set in a tiebreaker after failing to serve it out leading 5-4 before Kontaveit hit back to dominate the second set. The American rebounded and pulled away in the third to claim a hard-fought win.
Story of the match
Each player came off of straight-set wins in the first round and there was a significant buzz in the air for the first-ever meeting between the American and Estonian.
After each player held comfortably to open the match, it was Williams who had the first break chances, but Kontaveit was able to escape and take a 2-1 lead.
The American continued to be wasteful on break chances, squandering three more opportunities in the seventh game, but on her sixth chance two games later, an error by the Estonian gave Williams a 5-4 advantage.
Kontaveit was able to break back and the set would eventually be settled in a tiebreaker with the eighth point being decisive, the second seed erring again and an ace closed things out for the six-time champion on set point.
It was a runaway for the Estonian to start the second set as Kontaviet ripped off three straight games, showcasing her power game and after breaks were traded, she led 4-1.
Serving for the set, Kontaveit arrived at triple set point and on her second of those chances, she fired an ace to claim the set and even the match in what was one of the best sets of her career.
After taking a break between the second and third set, Williams drew first blood, converting on her third break point, taking a marathon second game following another unforced error by the Estonian to seemingly seize the momentum.
Uncharacteristically, the American let a 40-0 lead on her serve slip and Kontaveit was able to break back, but Williams broke once more and held to solidify her lead, which was now 4-1.
Having saved a break point, Williams closed out her service game with a winner that put her ahead 5-2 and a game later, she broke to love after pouncing on a second serve to extend her career at least another round.