The highest seed left in the women's draw, the two-time champion needed three hours, one minute to put away the pesky Dutchwoman, who became the fourth straight opponent to force Williams to three sets since the WTA Tour restarted.
Williams goes the distance to overcome Rus
Williams had the first break point of the match in the fourth game of the first set, but Rus was able to save the chance and kept pace with the American, although she faced deuce serving to stay in the set at 5-4 down.
The third seed lost just six points on her serve in the opening set, but she lost two of her first three points to fall behind 4-2. Williams rallied, saving a set point at 6-5 and three points later, she struck a forehand that Rus had no answer for.
There were three breaks in the first four games of the second set, Rus claiming a 3-1 advantage after forcing Williams to net a forehand. She stayed solid and a crosscourt backhand winner on her second set point levelled the match.
Williams saved four points in the opening game of the third set and she broke when Rus double-faulted to go in front 2-0. The Dutchwoman was in danger of falling behind a double break, but held on to stay in contact.
Incredibly, Rus ran off four straight games, capped with a forehand down the line for a clean winner and a 6-5 lead. Serving for the match, she came within two points of victory twice, but Williams broke back and then blanked the Dutchwoman to survive a tougher than expected test.