Wimbledon 2018: Serena Williams seeded No. 25 in London

June 27 (UPI) -- Despite her placement outside of the top 32 in the WTA rankings, Serena Williams enters Wimbledon with the No. 25 seed.

The seven-time tournament champ is the only player in the tournament, which starts July 2, not seeded with her WTA ranking. The Wimbledon referee announced the seedings Wednesday. Roger Federer is the top seed in men's singles, while Simona Halep is the No. 1 seed for the women.

Williams was denied a seed at the 2018 French Open. She was ranked No. 1 in the world when she took maternity leave, following her victory at the 2017 Australian Open. Wimbledon will be Williams' third tournament since giving birth to daughter Alexis Olympia in September.

The 23-time Grand Slam champion reached the fourth round at Roland Garros, but pulled out of the tournament due to a pectoral injury, sending Maria Sharapova into the next round. Sharapova is the No. 24 seed at Wimbledon.

Williams, 36, has been nostalgic throughout the week about her past success at the tournament, taking to social media to post about her achievements at Wimbledon.

"7 days until #Wimbledon⁠," Williams wrote Monday. "It's hard to believe it's been 16 years since my first title in London. What I remember most from that day is the genuine happiness and support from my competitor, big sister and best friend Venus Williams."

She posted again on Tuesday, posting a photo alongside Federer.

"15 years ago a boy from Switzerland and a girl from the US, both 21, shared the stage at Wimbledon for the first time ... and it wouldn't be the last," she wrote.

Dominika Cibulkova is ranked No. 32 in the world. She missed out on a seed at the tournament when Williams received her seed, pushing her out of the top 32 players at Wimbledon. Williams is ranked No. 183 in the WTA rankings.

No unseeded player has ever won the ladies singles tournament.

"I think it's just not fair," Cibulkova told reporters on Tuesday. "I have tried and I should be seeded. If they put her in front of me then I will lose my spot that I am supposed to have."

"I was a former number four, and it's also like why should I not be seeded if I have the right to be?"

According to Wimbledon's seeding guidelines, the order follows the WTA ranking list, "except where in the opinion of the committee, a change is necessary to produce a balanced draw."

There was no variation from the WTA rankings at the 2017 tournament.