Only time will tell if we have witnessed the final occasion that 45-year-old Venus Williams steps out at the US Open.

The American icon's performance in a gallant first-round defeat by Czech 11th seed Karolina Muchova suggested there is more mileage left in the tank.

But, at the end of a moving night, the seven-time Grand Slam champion did not want to look too far ahead.

Instead she reflected on how she has battled back from serious health issues to push the world's best players to their limit - against the odds.

"Getting back on the court was about giving myself a chance to play more healthy," Williams said in an emotional post-match news conference.

"When you play unhealthy, it's in your mind. It's not just how you feel. You get stuck in your mind too. So it was nice to be freer."

Williams tailed off in what proved to be her final answer, becoming visibly upset before the interview was cut short following a long silence.

In 2011, Williams was diagnosed with Sjogren's syndrome, an incurable autoimmune disease with symptoms including pain, numbness and fatigue.

Last month, she revealed how she had also been affected by the severity of painful fibroids - abnormal growths that develop in the uterus.

After Monday's 6-3 2-6 6-1 defeat, Williams remembered how she felt "uncomfortable" against the same opponent in a one-sided loss at the 2020 US Open.

"I wasn't well. I was in so much pain. Today it's night and day how much better I felt," Williams said.

"I'm so grateful to have had the opportunity to play feeling better."

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."

While Williams's future is unclear, there is clearly a strong chance this might be the last time she graces the US Open - and meant fans flocked to Flushing Meadows to pay tribute.

Dorothy Blagmon, originally from New York City but living in Atlanta since 1988, was unsure about attending this year due to her age.

The 79-year-old changed her mind when it was announced Williams was going to play.

"I've been a fan since Venus and Serena started playing tennis and their father was training them, and watched almost all their matches," she said.

"I might never get to see her again - not down to her not coming back but down to myself not being able to come here.

"I don't have poor health but, guess what, it's my age - I'm 80 in December.

"I love that she loves to play because I love tennis too - and I love her."

Using her height to generate power, Williams changed the face of the WTA Tour with her aggressive, first-strike tennis.

It became a blueprint for success - including her younger sister Serena, who went on to win 23 major titles.

The pair became a role model for a generation of African-American girls growing up in the late 1990s and early 2000s - as well as millions more of all ages.

Venus Williams further inspired fans by leading the fight for women's players to earn equal prize money, and the way she has prolonged her career in spite of her health problems.

"Venus is super-iconic," said Chanese Allen, a 32-year-old from Manhattan.

"I grew up watching her and have been playing since I was seven - when I saw her on the TV screens. It was amazing to see somebody I could relate to.

"To know I could do that possibly - I did train and play tournaments, although I didn't make it to the pro level - kept me going and is why I continue to keep playing."