Rus may have been inferior to the 23-time grandslam champion, but in the rally she was certainly not the inferior. In the tiebreak of the first set Rus even got a setpoint, at 6-5, but she did not manage to cash it.
though Rus lost her serve immediately in the second set, she did force a third set. That gave the Dutch instant four chances to break, but Williams held out and walked out to 4-1.
The top fit Russian came back and even served before the games at a 6-5 lead. Williams didn’t give up and didn’t give Rus any more points in the tiebreak.