Unfortunately, it wasn't game, set, match for the Royal Hen.

A true sports icon was sent home on The Masked Singer's Oct. 18 episode. After performing "Philadelphia Freedom" during Elton John night, the Royal Hen received the least amount of votes and was sent home.

As for which barrier-breaking athlete was behind the outlandish costume? It was none other than tennis legend Billie Jean King, who was the inspiration for John's 1975 song as she once played for the Philadelphia Freedoms professional tennis team.

"I am really lucky because he said, ‘I want to write you a song,' and I'm like ‘What? What?'" King said after the unmasking. "'That would be the greatest gift to the people of Philadelphia if you would do that.' If you go to Philadelphia, everybody is still playing it. It's their anthem."

Prior to the 79-year-old's reveal, viewers were given clues about her identity, including a nod to her history-making 1973 "Battle of the Sexes" victory over rival Bobby Riggs.

"For the first time ever, the Royal Hen is set to hold court," announced King's video package, a nod to her tennis background. "A true trailblazer, she is famous for championing equal opportunities for all and has made it her mission to be a voice for the voiceless. Her road to stardom was wrought with prejudice."

The final hint was that she received that Presidential Medal of Freedom from President Barack Obama.

Robin Thicke guessed Gloria Steinem, while Jenny McCarthy chose Rita Moreno and Nicole Scherzinger picked Dr. Ruth Westheimer. But once again, Ken Jeong was the only judge to correctly guess the celebrity underneath the mask and picked King.

After she removed her mask, King noted of her experience, "It was great but it is so hot. I'm sweating bullets!"

Keep reading to meet the whole cast and see who is still in the competition. The Masked Singer airs Wednesdays at 8 p.m. on Fox.

During the season 10 kickoff special on Sept. 10, Demi Lovato was revealed as Anonymouse. However, she won't be competiting, it was a special one-time appearance.

"I wanted to be on your show," she told host Nick Cannon during the episode, "because it seemed so fun, and it has been so fun. And I get to sing, so its the best of both worlds."

The Rubber Ducky was revealed as Black-ish actor Anthony Anderson on the Sept. 27 episode.

The Diver was exposed as Vanderpump Rules star Tom Sandoval on Oct. 4.

Michael Rapaport was unmasked as the Pickle on the Oct. 11 episode.

Tennis legend Billie Jean King was revealed to be the Royal Hen on the Oct. 18 episode.