American veteran Venus Williams says a dramatic fall that ruined her hopes of a notable Wimbledon win was "painful" and has left her "in shock".

Williams, 43, slipped early in the first-round match against Ukraine's Elina Svitolina, leading to fears she might have to retire injured.

The five-time champion did continue and pushed Svitolina before losing 6-4 6-3.

"It was bad luck for me," Williams said. "I can't believe it happened. I'm still trying to process it."

Williams, who started the match with heavy strapping on her right knee, showed undiminishing determination and courage to fight through her fitness problems before succumbing to 2019 semi-finalist Svitolina.

After a record 24th Open era appearance in the Wimbledon singles ended, Williams received a standing ovation by a crowd unsure how long she has left at the top level.

The fact she was able to finish the match, despite limping heavily around the court, felt remarkable.

Williams' defiance not to quit was warmly appreciated by the Wimbledon crowd, who willed her on throughout an entertaining contest.

The former world number one first played at the All England Club in 1997 and, as she remains coy about her retirement plans, it remains to be seen how many more times she will return to the scene of some of her greatest triumphs.

"What makes this one hard to process is I've had so many injuries. I've been missing from tour for quite a while. This is not what I want for myself," said Williams, who was playing in only her sixth match this year after being given a wildcard.

"This kind of fall, I didn't do anything wrong. I just went for the ball. There's nothing I can really do about it. Those kinds of things are hard to process emotionally, mentally and physically on the court."

Williams walked gingerly when she came out on to court, having struggled with the knee injury earlier in the British grass-court season at Birmingham.

The veteran showed she had lost none of her shot-making ability, using her colossal serve and forehand to good effect as she broke for a 2-0 lead.

"I was literally killing it, then I got killed by the grass. I felt like I was in great form and in great form in the match," Williams said.

The complexion of the match altered in a moment, leaving those watching on Centre Court fearing the worst.

In the third game, Williams slipped on the grass as she approached the net, letting out a sharp scream which silenced the stadium.

Umpire Marija Cicak raced down to the court to check on her condition, with a concerned Svitolina coming around the net.

There was an anxious atmosphere as fans feared the worst, many who will have remembered her younger sister Serena slipping on the lush Centre Court grass in 2021 and having to retire injured.

"I'm not sure what I've done. I'll have to investigate it. It was quite painful," Williams said.

"Afterwards it was very hard to focus on what I was doing."

In what seemed remarkable given the gravity of her reaction, and the increasingly-restricted movement, Williams not only carried on but continued to keep in touch with 28-year-old Svitolina.

Heavy shots reminiscent of her peak flashed past the Ukrainian, who had to fend off two break-back points before sealing the first set at the second opportunity.

Even when Svitolina, who is still continuing her comeback after giving birth last October, threatened to run away with the second set, Williams would not roll over.

Trailing 5-1 and with the crowd willing her on, she dug in again to hold serve and then broke for 5-3.

But Svitolina, who did well to maintain her focus in the difficult circumstances, took her opponent's serve again for the match after winning a line-call challenge that left Williams smiling ruefully.

"It is always very tough to play against Venus, it was a really special moment to play here today on a special court and a big legend," said Svitolina, who is ranked 76th in the world.

"It was an unbelievable feeling."