Alysha Tsuji

USA TODAY

Serena Williams' coach Patrick Mouratoglou tweeted out kind words of congratulations to both Williams and her fiancé Alexis Ohanian on Friday after it was reported that the tennis star gave birth.

Someone must have passed along the news to Mouratoglou, who was at the U.S. Open. He told Williams that he's happy for her and emphasized that he wishes her "a speedy recovery."

"We have a lot of work ahead of us," he added, playfully referring to her eagerness to get back on the court.

Last weekend, Mouratoglou said, per USA TODAY Sports:

"She (Serena Williams) tells me you have to find a hitting partner for me in September when I come back," Mouratoglou revealed, laughing. "I said, 'You are having the baby in September, you can find just someone to hand feed you balls.' She said to me, 'Don't underestimate me.' This is Serena." "The goal is to be ready for the Australian Open and then we'll see," said Mouratoglou, of Williams' desire to defend her title. "If she's ready, she'll compete. If not, we'll delay the comeback. I don't think she should compete if she's not really ready."

Williams won the 2017 Australian Open in January while she was eight weeks pregnant.

In Mouratoglou's message to Ohanian, he mentioned that he knows how the couple is feeling since he has three daughters of his own and that "each time it is the same incredible journey."