Serena Williams put on a show in the first round of the U.S. Open on Monday night, defeating Danka Kovinić in straight sets 6-3, 6-3.

Williams was playing in what is likely her final Grand Slam tournament. After the victory, Gayle King appeared at Arthur Ashe Stadium at one end of the court and introduced Williams to step up to the microphone.

King asked Williams why she decided it was time to walk away. Williams wrote an essay about walking away from the sport she dominated for a number of years. 

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"It’s been such a hard decision, you know. … It’s been a very hard decision because I think when you’re passionate about something, and you love something so much I think it’s always hard to walk away," Williams said. "Sometimes it’s harder to walk away than to not and that’s been the case for, so I’ve been trying to decide for a little while what to do."

The 23-time Grand Slam singles champion joked that the sport still kept her fit.

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"But I was just like, ‘Alright, I think now’s the time. I just have a family' … There’s other chapters in life and, you know, I call it an evolution," she said.

Williams admitted that "winning" at this stage would mean having success in her post-tennis career.

"I have my VC company, Serena Ventures, and like I said we invest in a lot of people. We invest in women and people of color and men as well, we invest in everyone. I really wanted to spend more time at home and work on my spiritual life and that was really important to me," she said.

"It’s like Serena 2.0. I’m still gonna be crazy, I’m still gonna be intense. I’ll still be around."

Williams looked as solid as ever against Kovinić, but will have a strong test in the second round Wednesday. Williams will face the No. 2-seeded Anett Kontaveit, who beat out Jaqueline Cristian in straight sets as well 6-3, 6-0.