Earlier this season, former world number one Williams was officially considered an inactive player, having gone a whole year without competing.
Then, out of nowhere as the eyes of the tennis world were trained on Wimbledon, Williams announced she was ready to play again at the Washington Open.
Williams beat 35th-ranked Peyton Stearns on her comeback in Washington, whetting her appetite for more competitive action.
Despite an opening defeat in Cincinnati, the two-time champion received a wildcard for a record-extending 25th appearance at the US Open.
Some argued putting a veteran with one victory in more than two years into the 128-woman draw blocked the development of a younger player.
Others believed an all-time great should always be offered the chance to compete.
Williams’ impressive level against Muchova answered the doubters – once she overcame a worrying start.
When she won only two of the opening 13 points, it felt like an ominous sign of things to come and led to a subdued atmosphere on Arthur Ashe Stadium.
A roar of encouragement arrived when Williams claimed her first point of the match, with the volume turning up as she started to gain a foothold.
Improving her service game proved key to the turnaround, acting as a confidence-builder which led to more fluent timing and movement.
The ball-striking was as clean and crisp as it had been for a long time.
But, given she had only played four matches in 18 months, Williams faded in a deciding set where Muchova sharpened up and served strongly.
Williams had proved a point. Yet she remained typically evasive when asked if she planned to more tournaments later this year.
“Are there any tournaments in the States? Can someone move a tournament here?” she asked.
“I don’t know that I’m willing to travel that far at this stage in my career to go play.
“I love playing. But my goal is to do what I want to do.”