A month after besting her sister Venus to win her seventh Australian Open, Serena Williams was back out on the court under the bright lights. While taking an evening constitutional with her fiancé Alexis Ohanian through San Francisco's Mission Dolores Park, the 23-time Grand Slam winner came across a couple of weekend warriors battling it out and decided she wanted to get in on the action.Serena narrated her journey on Snapchat, and TMZ preserved the video, as she considered approaching the guys and asking if she could play. She was curious to see how they'd react, if they'd notice her, but once she asked if she could get winner, one of the guys immediately made it clear he knew exactly who she was, saying "Oh my goodness…is this for real?"It was for real and even though Ohanian didn't film her actually hitting with them, she clearly did play (as did her puppo, Chip). She sounded kind of winded at the end of the video—maybe because she was playing in giant boots?—and said she was "still undefeated."h/t FTWThis is incredible. Imagine playing tennis and all of a sudden, the GOAT — Karlo Sy Su (@KarloSySu)February 27, 2017