Former President Barack and Michelle Obama were in attendance at the Arthur Ashe Stadium to witness Coco Gauff’s first-round victory over Laura Siegemund of Germany at the US Open and gave the tennis phenom some advice after the match after an exchange with a line judge, the Associated Press reports.

Gauff, 19, said she had no idea that the Obamas were in the stadium until the match was complete.

“I wasn’t sure they were here or not. I saw the Secret Service. I didn’t know if it was [President Joe] Biden and [First Lady Jill] Biden. I knew it was somebody. Then I heard that maybe [Bill] Clinton was coming. I didn’t know who exactly it was. So I didn’t know until after the match,” Gauff said on Monday (August 28).

The tennis superstar expressed that she was stunned when the Obamas asked to meet with her.

“I didn’t see them in the presidential box,” Gauff said. “I was obviously looking at that, but they weren’t, I guess, in my eyeline. But afterward, they told me they wanted to say hi.”

“Then Mr. Obama was there in the room, too. I was like, ‘Oh, my God,” Gauff continued, smiling from ear to ear at the news conference. “I haven’t soaked it in because I literally just walked in here. I think I’m going to never forget that moment for the rest of my life. I went from being really upset after a win to, like, being really happy. So I’m glad I got to meet them. They gave me some good advice, too.”

Gauff went on to say that Michelle Obama told her that “it’s good to speak up for myself. I think she was happy that I spoke up for myself today.”

During the match, Gauff complained to the line judges that Siegmund was taking too much time to play the next point. In the previous set, she was warned by chair umpire Marijana Veljovic for taking too long to begin the set.

"She's never ready when I'm serving. ... How is this fair?" Gauff explained to Veljovic. "I'm going at a normal speed. Ask any ref here. ... I've been quiet the whole match. ... Now it's ridiculous. I don't care what she's doing on her serve, but (on) my serve, she has to be ready."

Eventually, Siegmund was docked a point for her constant delays.

Not only did she get to enjoy Gauff’s victory as a spectator, but Michelle Obama also took part in a tribute to Billie Jean King in acknowledgement of the 50th anniversary of the U.S. Open becoming the first Grand Slam tennis tournament to award equal prize money to women.

“Billie Jean teaches us that when things lie in the balance, we all have a choice to make. We can either wait around and accept what we’re given. We can sit silently and hope someone else fights our battles. Or we can make our own stand,” “We can use whatever platforms we have to speak out and fight to protect the progress we’ve made, and level the playing field for all of our daughters and their daughters,” Michelle Obama said in her speech.

Gauff’s next opponent is Mirra Andreeva who she’ll face on August 30 (Wednesday) at 12 p.m EST.