(NEW YORK) -- All eyes were on Serena Williams as the tennis superstar made an electric first-round appearance in her final U.S. Open appearance before retirement.
Williams defeated 80th-ranked Danka Kovinic of Montenegro on center court in two sets, 6-3, 6-3.
Williams, 40, has been the talk of the tournament after she announced earlier this month in a personal essay for Vogue that her time as a pro was coming to a close.
Williams defeated Martina Hingis in the U.S. Open final to win her first major title in 1999 at the age of 17. Williams defeated five future Hall of Famers, including Hingis, to win that title.
In her 27 years, Williams has notched 23 major singles titles -- the most in the Open Era for men or women -- as well as 14 in doubles, two more in mixed doubles and four Olympic gold medals. Her 73 singles titles overall is fifth all time among women. Margaret Court holds the all-time majors record with 24. Her career began in 1960, and professional players were not allowed to compete until 1968, though she also won 11 majors in the Open Era.
Rennae Stubbs, her latest coach, longtime competitor, friend and six-time grand slam doubles winner, told "Good Morning America" on Monday that her goal was "to just keep her happy."
"She looks great. She's been practicing really, really hard," Stubbs said leading up to the opening match. "One of the things I emphasized with her when I did start working with her was, 'You got to play more sets against other players.' She hasn't played many matches in the last two years and had the injury at Wimbledon last year, therefore wasn't sure if she was going to come back. And I think she got the bug to finish the way she wanted to finish, which was on her terms. And she's done that now."
Ticket sales skyrocketed in the days after Williams announced she would be stepping away from tennis following the U.S. Open -- even before fans knew which night she would be playing.
Williams has been beset by injuries in recent years and hasn't played 10 tournaments in a year since 2015. In the last two years, she has lost to an opponent ranked No. 100 or worse three times. She sat out the 2021 U.S. Open as well as the first two majors in 2022. She hasn't played in a major final since 2019.
Williams is currently ranked 410th in the world and lost in the first round of Wimbledon in July.
She won her 23rd grand slam title -- besting Steffi Graf's 22 titles -- in January 2017 when she was pregnant with daughter, Alexis Olympia. She and Olympia wore matching Nike outfits Monday night.
Stubbs said she "didn't have the success that we're used to her having" in 2022 and noted that a lack of matches "really hurts" her play.
"Through the years she's always played so many matches, she hadn't had to play a lot of practice sets or play with any other players, so the emphasis on her over the last couple weeks is, 'Let's play some sets against great players.' At least you get that match practice, in practice, and she's done that and embraced it. So she's been really, really good."
Ultimately, Stubbs said "this is going to be a human moment for her tonight."
"To know the enormity of this match, her last ever match possibly -- or if she wins how excited everyone's going to be to see her play another match at the U.S. Open. The crowd is going to be amazing. You're not human if you don't feel the emotions," Stubbs said. "There's no doubt she will be very nervous going on the court -- anxiety level will be high because she always has [high] expectations."
Serena and her sister Venus were granted a wild card entry into the women's doubles tournament in Queens, New York -- a doubles title she's won twice with her sister. The women's doubles tournament opens up on Aug. 31 with the Williams sisters playing Czech players Linda Noskova and Lucie Hradecka in the first round.