Truly anything can happen in Dolores Park. On a stroll with her partner Alexis Ohanion, the co-founder of Reddit with whom she announced her engagement in December, tennis legend Serena Williams waltzed onto the park's courts to challenge two unsuspecting players.

"Can I play winner?" Williams asks. This is devastating stuff.

TMZ has it that Williams joined the duo on court for some pics and a few shots. With knee-high boots instead of tennis shoes, she opted not to play a full set, but let's just award her the win, shall we? I mean, we're talking "greatest of all time."

Below, some footage from USA Today sports reporter Alysha Tsuji.

Related: Serena Williams Announces Engagement To Reddit Co-Founder In Reddit Post