Six-time winner Serena Williams reached the US Open quarter-finals with a 6-0 4-6 6-3 victory over Kaia Kanepi.
Williams, 36, took the first set in only 18 minutes as she converted all three break points she earned, and did not drop a point on her first serve.
But Estonia's Kanepi responded, displaying some of the shot-making that helped her beat world number one Simona Halep in the first round.
Williams broke early in the next as she completed her win in 97 minutes.
The 23-time Grand Slam singles champion will now play Czech eighth seed Karolina Pliskova.